Download Virtual ChemLab Record Sheets

4573_PH_CHEM_FM_ppi-iv 8/11/04 11:58 AM Page i
PREN TIC E HALL
Virtual ChemLab
Record Sheets
Needham, Massachusetts
Upper Saddle River, New Jersey
4573_PH_CHEM_FM_ppi-iv 8/11/04 11:58 AM Page ii
Copyright © by Pearson Education, Inc., publishing as Pearson Prentice Hall, Upper Saddle River, New Jersey 07458.
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ISBN 0-13-166227-9
1 2 3 4 5 6 7 8 9 10
07 06 05 04 03
4573_PH_CHEM_FM_ppi-iv
8/12/04
2:00 PM
Page iii
Contents
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Installing Virtual ChemLab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Lab 1: Flame Tests for Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Lab 2: Names and Formulas of Ionic Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Lab 3: Counting by Measuring Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Lab 4: Thomson Cathode Ray Tube Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Lab 5: Millikan Oil Drop Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Lab 6: Atomic Structure: Rutherford’s Experiment . . . . . . . . . . . . . . . . . . . . . . . . . 14
Lab 7: Atomic Emission Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Lab 8: Photoelectric Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Lab 9: Diffraction Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Lab 10: Electronic State Energy Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Lab 11: Pressure-Volume Relationship for Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Lab 12: Temperature-Volume Relationship for Gases . . . . . . . . . . . . . . . . . . . . . . . . 30
Lab 13: Derivation of the Ideal Gas Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Lab 14: Ideal vs Real Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Lab 15: Investigation of Gas Pressure and Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Lab 16: The Specific Heat of a Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Lab 17: Heat of Fusion of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Lab 18: Heats of Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Lab 19: Heat of Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Lab 20: Enthalpy and Entropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Lab 21: Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
iii
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Lab 22: Precipitation Reactions: Formation of Solids . . . . . . . . . . . . . . . . . . . . . . . . 53
Lab 23: Identification of Cations in Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Lab 24: Qualitative Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Lab 25: Study of Acid-Base Titrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Lab 26: Acid-Base Titrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Lab 27: Ionization Constants of Weak Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Lab 28: Analysis of Baking Soda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Lab 29: Molecular Weight Determination by Acid-Base Titration . . . . . . . . . . . . . . 70
Lab 30: Redox Titrations: Determination of Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
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iv
Contents
4573_PH_CHEM_FM_ppi-iv 8/11/04 11:58 AM Page v
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Overview
Welcome to Virtual ChemLab for Prentice Hall Chemistry, a set of realistic and
sophisticated simulations covering topics in general chemistry. In these
laboratories, students are put into a virtual environment where they are free to
make the choices and decisions that they would confront in an actual laboratory
setting and, in turn, experience the resulting consequences. These laboratories
include simulations of inorganic qualitative analysis, fundamental experiments
in quantum chemistry, gas properties, titration experiments, and calorimetry.
This version of Virtual ChemLab is intended to be used in conjunction with the
Prentice Hall Chemistry Virtual ChemLab Record Sheets, which contains 30
laboratory assignments covering the topics of stoichiometry, atomic theory, gas
properties, thermodynamics, chemical properties, acid-base chemistry, and
electrochemistry. Many of these “virtual” laboratory assignments can also be
found as “real” assignments in the Student Editior or accompanying Laboratory
Manual, but there are also a significant number of new assignments, such as
Thomson’s cathode ray tube experiment and the Millikan oil drop experiment,
which will provide students the opportunity to perform experiments not
previously available to them.
The general features of the inorganic simulation include 26 cations that can
be added to test tubes in any combination, 11 reagents that can be added to the
test tubes in any sequence and any number of times, necessary laboratory
manipulations, a lab book for recording results and observations, and a
stockroom for creating test tubes with known mixtures, generating practice
unknowns, or retrieving instructor assigned unknowns. The simulation uses
over 2,500 actual pictures to show the results of reactions and over 220 videos
to show the different flame tests. In all, there are in excess of 1016 possible
outcomes for these simulations.
The purpose of the quantum laboratory is to allow students to explore and
better understand the foundational experiments that led to the development
of quantum mechanics. Because of the very sophisticated nature of most of
these experiments, the quantum laboratory is the most “virtual” of the Virtual
ChemLab laboratory simulations. In general, the laboratory consists of an optics
table where a source, sample, modifier, and detector combination can be
placed to perform different experiments. These devices are located in the
stockroom and can be taken out of the stockroom and placed in various
locations on the optics table. The emphasis here is to teach students to probe
a sample (e.g., a gas, metal foil, two-slit screen, etc.) with a source (e.g., a laser,
electron gun, alpha-particle source, etc.) and detect the outcome with a specific
detector (e.g., a phosphor screen, spectrometer, etc.). Heat, electric fields, or
magnetic fields can also be applied to modify an aspect of the experiment. As
in all Virtual ChemLab laboratories, the focus is to allow students the ability to
explore and discover, in a safe and level-appropriate setting, the concepts that
are important in the various areas of chemistry.
The gas experiments included in the Virtual ChemLab simulated laboratory
allow students to explore and better understand the behavior of ideal gases,
real gases, and van der Waals gases (a model real gas). The gases laboratory
contains four experiments each of which includes the four variables used to
describe a gas: pressure (P), temperature (T), volume (V), and the number of
Overview
v
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vi
Overview
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moles (n). The four experiments differ by allowing one of these variables to be
the dependent variable while the others are independent. The four
experiments include (1) V as a function of P, T, and n using a balloon to reflect
the volume changes; (2) P as a function of V, T, and n using a motor driven
piston; (3) T as a function of P, V, and n again using a motor driven piston; and
(4) V as a function of P, T, and n but this time using a frictionless, massless
piston to reflect volume changes and using weights to apply pressure. The
gases that can be used in these experiments include an ideal gas; a van der
Waals gas with parameters that can be changed to represent any real gas; real
gases including N2, CO2, CH4, H2O, NH3, and He; and eight ideal gases with
different molecular weights that can be added to the experiments to form gas
mixtures.
The virtual titration laboratory allows students to perform precise,
quantitative titrations involving acid-base and electrochemical reactions. The
available laboratory equipment consists of a 50 mL buret, 5, 10, and 25 mL pipets,
graduated cylinders, beakers, a stir plate, a set of 8 acid-base indicators, a pH
meter/voltmeter, a conductivity meter, and an analytical balance for weighing
out solids. Acid-base titrations can be performed on any combination of mono-,
di-, and tri-protic acids and mono-, di-, and tri-basic bases. The pH of these
titrations can be monitored using a pH meter, an indicator, and a conductivity
meter as a function of volume, and this data can be saved to an electronic lab book
for later analysis. A smaller set of potentiometric titrations can also be performed.
Systematic and random errors in the mass and volume measurements have been
included in the simulation by introducing buoyancy errors in the mass
weighings, volumetric errors in the glassware, and characteristic systematic and
random errors in the pH/voltmeter and conductivity meter output. These errors
can be ignored, which will produce results and errors typically found in high
school-level laboratory work, or the buoyancy and volumetric errors can be
measured and included in the calculations to produce results better than 0.1% in
accuracy and reproducibility.
The calorimetry laboratory provides students with three different
calorimeters that allow them to measure various thermodynamic processes
including heats of combustion, heats of solution, heats of reaction, the heat
capacity, and the heat of fusion of ice. The calorimeters provided in the
simulations are a classic “coffee cup” calorimeter, a dewar flask (a better
version of a coffee cup), and a bomb calorimeter. The calorimetric method used
in each calorimeter is based on measuring the temperature change associated
with the different thermodynamic processes. Students can choose from a wide
selection of organic materials to measure the heats of combustion; salts to
measure the heats of solution; acids, bases, oxidants, and reductants for heats
of reaction; metals and alloys for heat capacity measurements; and ice for a
melting process. Temperature versus time data can be graphed during the
measurements and saved to the electronic lab book for later analysis.
Systematic and random errors in the mass and volume measurements have
been included in the simulation by introducing buoyancy errors in the mass
weighings, volumetric errors in the glassware, and characteristic systematic
and random errors in the thermometer measurements.
4573_PH_CHEM_FM_ppi-iv 8/11/04 11:58 AM Page vii
Installing Virtual ChemLab
Locate and run the program “Setup ChemLab” (which is located in the
appropriate operating system folder—“Mac” or “Windows”) on the CD-ROM
drive then follow the prompts. The CD is not needed to run the program.
Important Installation Notes and Issues
1. The graphics used in the simulations require the monitor to be set to
24-bit true color (millions of colors). Lower color resolutions can be
used, but the graphics will not be as sharp.
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2. In the directory where Virtual ChemLab is installed, the user must always
have read/write/erase privileges to that directory and all directories
underneath. This condition is initially set by the installer, but this may
have to be reset manually if the system crashes hard while running
Virtual ChemLab. This is generally only a problem with the OSX
operating system if multiple users login to the same OSX machine. This
can also be a problem with advanced Windows operating systems if the
user is not a Power User or higher.
3. When multiple users access the same installed software on a given
computer, file ownership and read/write privileges becomes a serious
issue since Virtual ChemLab shares some files among users to a certain
degree depending on the installation. (a) In a direct access installation or
when multiple users on a network drive share the database, all users
must have complete read/write/erase privileges to the directory (and
all directories underneath) where the database is stored. (b) In a web
connectivity installation, either (i) the same computer login must be
used for all ChemLab users (so file ownership is the same for all database
files) or (ii) each user who creates a local ChemLab account (or new
ChemLab user) must use the same computer login as when the account
was created in order to maintain file ownership consistency. This will
only be a problem with OSX machines and Windows operating systems
using Restricted Users.
4. When using Virtual ChemLab under the Windows 2000 Professional or
higher operating systems, users must be, at a minimum, a Power User in
order for the program to have sufficient rights to run properly. The
program will run as a Restricted User but the fonts will be incorrect
along with other minor annoyances. In a server environment where a
Restricted User is necessary, we suggest that a separate ChemLab
Account be setup, which gives the user Power User Status but only
gives the user access to the ChemLab software. This is a Macromedia
Director limitation.
Installing Virtual ChemLab
vii
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5. Occasionally on all Windows platforms, the Virtual ChemLab installer
will fail to load and execute. This can be corrected by going to
www.javasoft.com and downloading and then installing the most recent
version of the java runtime software. The Virtual ChemLab installation
software is a java based application.
6. QuickTime 5.0 or later is required for the software to run properly. The
most recent version of QuickTime can be obtained at
http://www.apple.com/quicktime/
7. When the simulation software has been installed on a Windows 2000
Professional operating system, there is better performance and better
system stability when the Windows 2000 Support Pack 2 has been
installed.
8. For unknown reasons, on some machines the QuickTime videos will
not play properly if the system QuickTime settings are in their default
state. This can be corrected by changing the Video Settings in
QuickTime to Normal Mode.
9. Printing in Virtual ChemLab does not work inside the OSX operating
system.
10. There are occasional spontaneous shutdowns of the software in OSX.
There are no known causes for this, but it appears to be a Macromedia
Director issue.
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viii Getting Started
4573_PH_CHEM_FM_ppi-iv 8/11/04 11:58 AM Page ix
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Getting Started
Virtual ChemLab is launched by clicking on the VCL icon located on the desktop
or in the Start Menu for Windows operating systems or on the Dock for the
Macintosh OS X operating system. After the startup, students will be brought
to a hallway containing three doors and a workbook sitting on a table. Clicking
on the electronic workbook opens and zooms into the workbook pages where
students can select preset assignments that correspond to the assignments in
the Prentice Hall Chemistry Virtual ChemLab Record Sheets. The Previous and Next
buttons are used to page through the set of assignments, and the different
assignments can also be accessed by clicking on the section titles located on
the left page of the workbook. Clicking on the Enter Laboratory button will
allow the students to enter the general chemistry laboratory (see below), and
the Exit button is used to leave Virtual ChemLab.
From the hallway, students can also enter the general chemistry laboratory
by clicking on the General Chemistry door. Once in the laboratory, students
will find five different laboratory benches that represent the five different
general chemistry laboratories. Rolling the mouse over each of these laboratory
benches pops up the name of the selected laboratory. To access a specific
laboratory, click on the appropriate laboratory bench. While in the general
chemistry laboratory, the full functionality of the simulation is available, and
students can explore and perform experiments as dictated by their instructors
or by their own curiosity. The Exit signs in the general chemistry laboratory
are used to return to the hallway.
Detailed instructions on how to use each of the five laboratory simulations
can be found in the user guides located in the Virtual ChemLab installation
directory. These same user guides can also be accessed inside each laboratory
by clicking on the Pull-Down TV and clicking on the Help button.
Contents
ix
4573_PH_CHEM_Lab01_pp001-003 8/11/04 12:24 PM Page 1
Name ___________________________
Date ___________________
Class _____________
Lab 1: Flame Tests for Metals
Purpose
To observe and identify metallic ions using flame tests.
Flame Tests
for Metals
Background
The characteristic yellow of a candle flame comes from the glow of burning
carbon fragments. The carbon fragments are produced by the incomplete
combustion reaction of the wick and candle wax. When elements, such as
carbon, are heated to high temperatures, some of their electrons are excited
to higher energy levels. When these excited electrons fall back to lower
energy levels, they release excess energy in packages of light called
photons, or light quanta.
The color of the emitted light depends on its energy. Blue light is more
energetic than red light, for example. When heated, each element emits a
characteristic pattern of light energies, which is useful for identifying the
element. The characteristic colors of light produced when substances are
heated in the flame of a gas burner are the basis of flame tests for several
elements.
In this experiment, you will perform the flame tests used to identify
several metallic elements.
Procedure
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1. Start Virtual ChemLab and select Flame Tests for Metals from the list of
assignments. The lab will open in the Inorganic laboratory.
2. Enter the stockroom by clicking inside the Stockroom window. Once
inside the stockroom, drag a test tube from the box and place it on the
metal test tube stand. You can then click on a bottle of metal ion solution
on the shelf to add it to the test tube. When you have added one metal
ion, click Done to send the test tube back to the lab. Continue doing this
until you have sent one test tube for each the following metal ions to the
lab: Na, K, Ca2, Ba2, Sr2, and Cu2.
3. On the right end of the supply shelf is a button labeled Unknowns. Click
on the Unknowns button to create a test tube with an unknown. Now
click on each of the following bottles on the shelf: Na, K, Ca2, Ba2,
Sr2, and Cu2. Do not change the maximum and minimum on the left
side. Click Save. An unknown test tube titled Practice will show in the
blue rack. Drag the practice unknown test tube from the blue rack to
place it in the metal stand and click Done. Now click on the Return to Lab
arrow.
Flame Tests for Metals
1
4573_PH_CHEM_Lab01_pp001-003 8/11/04 12:24 PM Page 2
Flame Tests
for Metals
Name ___________________________
Date ___________________
Class _____________
4. When you return to the lab you should note that you have seven test
tubes. You will use two of the buttons across the bottom, Flame and
Flame w/ Cobalt (blue glass held in front of the flame.) A test tube must be
moved from the blue test tube rack to the metal test tube stand in order
to perform the flame test. You can drag a test tube from the blue rack to
the metal test tube stand to switch places with a test tube in the metal
test tube stand. Just above the periodic table there is a handle. Click on
the handle to pull down the TV monitor. With the monitor down you
can mouse-over each test tube and it will identify what metal ion the test
tube contains. As you mouse over each test tube, you will also see a
picture of what it contains in the lower left corner. One of your test tubes
is labeled Practice and when you mouse over it, the TV monitor tells you
it is an unknown.
5. Select the test tube containing Na and place it on the metal stand. Click
the Flame button. Record your observations in the data table below. Click
the Flame w/Cobalt button and record your observations in the same
table.
6. Drag the K test tube to the metal stand to exchange it with the Na.
Flame test K with and without cobalt glass. Record your observations
in the table below.
7. For the other four ions, Flame test them only. Do not use cobalt glass.
Record your observations in the table below.
sodium, Na
sodium, Na (cobalt glass)
potassium, K
potassium, K (cobalt glass)
calcium, Ca2
barium, Ba2
strontium, Sr2
copper, Cu2
unknown #1
unknown #2
unknown #3
unknown #4
2
Flame Tests for Metals
Flame Color
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Ion
4573_PH_CHEM_Lab01_pp001-003 8/11/04 12:24 PM Page 3
Name ___________________________
Date ___________________
Class _____________
Flame Tests
for Metals
8. Flame test the practice unknown. Determine which of the six metal ions
it most closely matches. You may repeat the flame test on any of the six
metal ions if necessary. When you are confident that you have identified
the unknown, open the Lab Book by clicking on it. On the left page, click
the Report button. On the right page, click on the metal ion that you
think is in the practice unknown. Click Submit and then OK. If all of the
ion buttons turn green you have successfully identified the unknown. If
any turn red then you were incorrect. Flame test the practice unknown
again to correctly identify your metal ion. Click on the red disposal
bucket to clear all of your samples.
Analysis and Conclusions
1. The energy of colored light increases in the order red, yellow, green,
blue, violet. List the metallic elements used in the flame tests in
increasing order of the energy of the light emitted.
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2. What is the purpose of using the cobalt glass in the identification of
sodium and potassium?
Flame Tests for Metals
3
4573_PH_CHEM_Lab02_pp004-005 8/11/04 12:18 PM Page 4
Name ___________________________
Date ___________________
Class _____________
Lab 2: Names and Formulas of
Ionic Compounds
Purpose
To observe the formation of compounds and write their names and
formulas.
Procedure
Names and Formulas of
Ionic Compounds
1. Start Virtual ChemLab and select Names and Formulas of Ionic Compounds
from the list of assignments. The lab will open in the Inorganic
laboratory.
2. Enter the stockroom by clicking inside the Stockroom window. Once
inside the stockroom, drag a test tube from the box and place it on the
metal test tube stand. You can then click on the bottle of Ag+ ion solution
on the shelf to add it to the test tube. Click Done to send the test tube
back to the lab. Click on the Return to Lab arrow.
4. Place a second tube from the blue rack on the metal stand. Add Na2SO4.
Record your observations and discard the tube. Use the next tube but
add NaCl, and record your observations. Use the next tube but add
NaOH, and record your observations. With the last tube add Na2CO3 and
record your observations. When you are completely finished, click on
the red disposal bucket to clear the lab.
5. Return to the stockroom and repeat steps 2–4 for Pb2, Ca2, Fe3, and
Cu2. Complete the table below.
Analyze
Each cell should include a description of what you observed when the
reagents were mixed and a correct chemical formula and name for all
solutions which turned cloudy and NR for all solutions which remained
clear. Remember to include roman numerals where appropriate.
4
Names and Formulas of Ionic Compounds
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3. Place the test tube containing the Ag+ solution in the metal test tube
stand. Click on the Divide button on the bottom (with the large red
arrow) four times to make four additional test tubes containing Ag+.
With one test tube in the metal stand and four others in the blue rack,
click on the Na2S bottle located on the lab bench. You will be able to
observe what happens in the window at the bottom left. Record your
observation in the table below and write a correct chemical formula and
name for the product of the reaction. If the solution remains clear, record
NR, for no reaction. Drag this test tube to the red disposal bucket on the
right.
4573_PH_CHEM_Lab02_pp004-005 8/11/04 12:18 PM Page 5
Name ___________________________
Ag
Pb2
Date ___________________
Ca2
Fe3
Class _____________
Cu2
Na2S
(S2)
Na2SO4
(SO42)
Names and Formulas of
Ionic Compounds
NaCl
(Cl)
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NaOH
(OH)
Na2CO3
(CO32)
Names and Formulas of Ionic Compounds
5
4573_PH_CHEM_Lab03_pp006-008 8/11/04 12:08 PM Page 6
Name ___________________________
Date ___________________
Class _____________
Lab 3: Counting by Measuring Mass
Purpose
Determine the mass of several samples of chemical elements and
compounds and use the data to count atoms.
Procedure
Start Virtual ChemLab and select Counting by Measuring Mass from the list of
assignments. The lab will open in the Calorimetry laboratory.
Part 1, Measuring Metal
1. Click on the Stockroom. Click on the Metals sample cabinet. Open the top
drawer by clicking on it. When you open the drawer, a petri dish will
show up on the counter. Place the sample of gold (Au) in the sample
dish by double-clicking on it. Zoom Out. Double-click on the petri dish to
move it to the stockroom counter. Click the green arrow to Return to Lab.
2. Drag the petri dish to the spotlight near the balance. Click on the Balance
area to zoom in. Drag the gold sample to the balance pan and record the
mass in Table 1.
3. Click on the red disposal bucket to clear the lab after each sample. Repeat
for lead (Pb), uranium (U), sodium (Na) and a metal of your choosing.
Table 1
lead (Pb)
Counting by
Measuring Mass
Mass
(grams)
Molar Mass
(g/mol)
Moles of
each element
Atoms of
each element
6
Mollusks, by
Counting
Arthropods,
Measuringand
Mass
Echinoderms
uranium (U)
sodium (Na)
Your Choice
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gold (Au)
4573_PH_CHEM_Lab03_pp006-008 8/11/04 12:08 PM Page 7
Name ___________________________
Date ___________________
Class _____________
Analyze
1. Calculate the moles of Au contained in the sample and enter into Table 1.
2. Calculate the atoms of Au contained in the sample and enter into Table 1.
3. Repeat steps 1 and 2 for the other metals and fill in the table. Clear the
laboratory when you are finished by clicking on the disposal bucket.
Part 2, Measuring Compounds
1. Click on the Stockroom. Double-click on sodium chloride (NaCl) on the
Salts shelf. The right and left arrows allow you to see additional bottles.
2. Return to Lab. Move the sample bottle to the spotlight near the balance
area. Click on the Balance area to zoom in and open the bottle by clicking
on the lid (Remove Lid). Drag a piece of weigh paper to the balance pan
and Tare the balance.
4. Repeat steps 1-3 for table sugar (sucrose, C12H22O11), NH4Cl, C6H5OH
(phenol), and a compound of your choice. Record the mass of each
sample in Table 2.
Counting by
Measuring Mass
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3. Pick up the Scoop and scoop out some sample; as you drag your cursor
and the scoop down the face of the bottle it picks up more. Select the
largest sample possible and drag the scoop to the weigh paper until it
snaps in place which will place the sample on the paper. Record the
mass of the sample in Table 2.
Table 2
NaCl
C12H22O11
NH4Cl
C6H5OH
Your Choice
Mass
(grams)
Molar Mass
(g/mol)
Moles of
each element
Atoms of
each element
Mollusks, Arthropods,
Counting byand
Measuring
Echinoderms
Mass
7
4573_PH_CHEM_Lab03_pp006-008 8/11/04 12:08 PM Page 8
Name ___________________________
Date ___________________
Class _____________
Analyze
1. Calculate the moles of C12H22O11 contained in the sample and record
your results in Table 2.
2. Calculate the moles of each element in C12H22O11 and record your
results in Table 2.
3. Calculate the atoms of each element in C12H22O11 and record your
results in Table 2.
4. Repeat steps 1–3 for the other compounds and record your results in
Table 2.
5. Which of the compounds contains the most total atoms?
Counting by
Measuring Mass
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8
Counting by Measuring Mass
4573_PH_CHEM_Lab04_pp009-010 8/11/04 12:07 PM Page 9
Name ___________________________
Date ___________________
Class _____________
Lab 4: Thomson Cathode Ray Tube
Experiment
Purpose
To duplicate the Thomson cathode ray tube experiment and calculate from
collected data the charge to mass ratio (q/me) of an electron.
Background
As scientists began to examine atoms, their first discovery was that they
could extract negatively charged particles from atoms. They called these
particles electrons. In order to understand the nature of these particles, they
wanted to know how much charge they carried and how much they
weighed. In 1897, John J. Thomson showed that if you could measure how
much a beam of electrons were bent in an electric field and in a magnetic
field, you could determine the charge to mass ratio (q/me) for the particles
(electrons). Knowing the charge to mass ratio (q/me) and either the charge
on the electron or the mass of the electron would allow you to calculate the
other. Thomson could not obtain either in his cathode ray tube experiments
and had to be satisfied with just the charge to mass ratio.
Procedure
2. What source is used in this experiment? (The source is on the left.
Drag your cursor over it to identify it.)
What type of charge do electrons have?
What detector is used in this experiment?
3. Turn on the Phosphor Screen. What do you observe?
4. Drag the lab window down and left and the phosphor screen window
up and right in order to be able to minimize overlap. Push the Grid
button on the phosphor screen, and set the Magnetic Field to 30 T.
(Click the button above the tens place three times.) What happens to the
spot from the electron gun on the phosphor screen?
Thomson Cathode Ray Tube Experiment
Thomson Cathode Ray
Tube Experiment
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1. Start Virtual ChemLab and select Thomson Cathode Ray Tube Experiment
from the list of assignments. The lab will open in the Quantum
laboratory.
9
4573_PH_CHEM_Lab04_pp009-010 8/11/04 12:07 PM Page 10
Name ___________________________
Date ___________________
Class _____________
5. Set the Magnetic Field back to zero and set the Electric Field to 10 V. What
happens to the spot from the electron gun on the phosphor screen?
Where should the signal on the phosphor screen be if the electric and
magnetic forces are balanced?
6. Increase the voltage of the Electric Field to move the spot several
centimeters from the center. To make your measurements more accurate,
move the spot until it aligns with a grid marking. What is the voltage?
What is the distance from the center that the spot has moved (in cm)?
7. Increase the magnetic field strength until the spot reaches the center of
the screen. What magnetic field creates a magnetic force that balances
the electric force?
Summarize your data.
deflected distance (d)
electric field (V)
magnetic field (B)
q>me (5.0826 1012) # V # d>B2
where V the electric field in volts, d the deflected distance from
center in cm, and B magnetic field in T.
What is your calculated value for the charge to mass ratio for an electron
(q/me)?
Thomson Cathode Ray
Tube Experiment
The modern accepted value is 1.76 1011. Calculate your percent error
as follows:
% Error 10
0 your value accepted value 0
100
accepted value
Thomson Cathode Ray Tube Experiment
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8. In a simplified and reduced form, the charge to mass ratio (q/me) can be
calculated as follows:
4573_PH_CHEM_Lab05_pp011-013 8/11/04 12:07 PM Page 11
Name ___________________________
Date ___________________
Class _____________
Millikan Oil Drop
Experiment
Lab 5: Millikan Oil Drop Experiment
Purpose
If you want to know either the charge or the mass of an electron, you need
to have a way of measuring one or the other independently. In 1909, Robert
Millikan showed that he could make very small oil drops and deposit
electrons on these drops (1 to 10 electrons per drop). He would then
measure the total charge on the oil drops by deflecting the drops with an
electric field. You will get a chance to repeat his experiments, and, using the
results from Lab 4, be able to experimentally calculate the mass of an
electron.
Procedure
1. Start Virtual ChemLab and select Millikan Oil Drop Experiment from the
list of assignments. The lab will open in the Quantum laboratory.
2. What source is used in this experiment?
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How does this source affect the oil droplets in the oil mist chamber?
3. The detector in this experiment is a video camera with a microscopic
eyepiece attached to view the oil droplets. Click the On/Off switch
(red/green light) to turn the video camera on. What do you observe on
the video camera screen?
What force causes the drops to fall?
The oil drops fall at their terminal velocity, which is the maximum
velocity possible due to frictional forces such as air resistance. The
terminal velocity is a function of the radius of the drop. By measuring
the terminal velocity (vt) of a droplet, the radius (r) can be calculated.
Then the mass (m) of the drop can be calculated from its radius and the
density of the oil. Knowing the mass of the oil droplet will allow you to
calculate the charge (q) on the droplet.
4. Measure the terminal velocity of a drop. Select a small drop that is falling
near the center scale and Click the Slow Motion button on the video
camera window when the drop appears at the top of the window. Wait
until the drop is at a tick mark and start the timer. Let the drop fall for at
least two or more tick marks and stop the timer. Do not let the drop fall
off the end of the viewing scope. Each tick mark is 0.125 mm. Record the
distance and the time in the data table below.
Millikan Oil Drop Experiment
11
4573_PH_CHEM_Lab05_pp011-013 8/11/04 12:07 PM Page 12
Millikan Oil Drop
Experiment
Name ___________________________
Date ___________________
Class _____________
5. Measure the voltage required to stop the fall of the drop. You now need to
stop the fall of the drop by applying an electric field between the two
voltage plates. Click on the buttons on the top or bottom of the Electric
Field until the voltage is adjusted and the drop stops falling. This should
be done while in slow motion. When the drop appears stopped, turn
slow motion off and do some final adjustments until the drop has not
moved for at least one minute. Record the voltage, V, indicated on the
voltage controller.
Drop
Voltage
(V, in volts)
Time
(t, in seconds)
Distance
(d, in meters)
1
2
3
6. Calculate the terminal velocity and record the value. Calculate the terminal
velocity, vt, in units of ms using this equation:
d
vt t , where d is the distance the drop fell in meters and t is the
elapsed time in seconds.
7. Calculate the radius (r) of the drop and record the value. With the
terminal velocity, you can calculate the radius of the using this equation:
r (9.0407 105m1>2 # s1>2) "vt (9.0407 105"vt, without units)
8. Calculate the mass of the drop and record the value. You can use the
answer from your previous answer for r to calculate the mass of the drop
given the density of the oil. The final equation to calculate the mass is
m Voil # roil 4p>3 # r 3 # 821kg # m3
(3439.0kg # m3) # r 3
(3439.0 r 3 , without units)
9. The force due to gravity must be the same as the force due to the
electric field acting on the electrons stuck to the drop: qE mg. Using
this equation, calculate the total charge (Qtot) on the oil drop due to the
electrons using the equation:
Qtot Q(n) # e (9.810 102C # kg 1 # J 1 # m>V (9.81 102 m/V,
without units)
12
Millikan Oil Drop Experiment
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Each of the equations in steps 7–9 are shown with units and without.
You will find it easier to use the equation without units for your
calculations.
4573_PH_CHEM_Lab05_pp011-013 8/11/04 12:07 PM Page 13
Name ___________________________
Date ___________________
Class _____________
where Q(n) is the number of electrons on the drop, e is the fundamental
electric charge of an electron, m is the mass calculated in #9, and V is
the voltage.
Millikan Oil Drop
Experiment
This answer will provide the total charge on the drop (Qtot). The
fundamental electric charge of an electron (e) is 1.6 1019 C
(coulombs). Divide your total charge (Qtot) by e and round your answer
to the nearest whole number. This is the number of electrons (Q(n)) that
adhered to your drop. Now divide your total charge (Qtot) by Q(n) and
you will obtain your experimental value for the charge on one electron.
10. Complete the experiment and calculations for at least three drops and
summarize your results in the data table.
Drop #
Terminal Velocity
(v t, in m/s)
Radius
(r, in meters)
Mass
(m, in kg)
Total charge
on drop
(Qtot, in
Coulombs)
Charge on one
electron (C)
1
2
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3
11. Average your results for the charge on one electron. Calculate the
percent error by:
0 your answer 1.6 1019 0
% Error 100%
1.6 1019
What is your average charge for an electron?
What is your percent error?
12. You will recall that in the Thomson experiment you were able to
calculate the charge-to-mass ratio (q/me) as 1.7 1011. Using this value
for q/me and your average charge on an electron, calculate the mass of
an electron in kg.
What is your calculated value for the mass of an electron in kg?
Millikan Oil Drop Experiment
13
4573_PH_CHEM_Lab06_pp014-016 8/11/04 12:07 PM Page 14
Name ___________________________
Date ___________________
Class _____________
Lab 6: Atomic Structure:
Rutherford’s Experiment
Purpose
To discover how the physical properties, such as size and shape, of an
object can be measured by indirect means and to duplicate the gold foil
experiment of Ernest Rutherford.
Atomic Structure:
Rutherford’s Experiment
Background
Procedure
1. Start Virtual ChemLab and select Atomic Structure: Rutherford’s Experiment
from the list of assignments. The lab will open in the Quantum
laboratory.
2. The experiment will be set up on the lab table. Point the cursor arrow to
the gray box on the left side. What particles are emitted from this source?
What are alpha particles?
3. Point the cursor arrow at the base of the metal sample stand (in the
center) and squeeze the mouse. What metal foil is used?
14
Mollusks,
Atomic
Structure:
Arthropods,
Rutherford’s
and Echinoderms
Experiment
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A key experiment in understanding the nature of atomic structure was
completed by Ernest Rutherford in 1911. He set up an experiment that
directed a beam of alpha particles (helium nuclei) through a gold foil and
then onto a detector screen. According to the plum pudding atomic model,
scientists thought electrons floated around inside a cloud of positive
charge. Based on this model, Rutherford expected that almost all the alpha
particles should pass through the gold foil and not be deflected. A few of
the alpha particles would experience a slight deflection due to the
attraction to the negative electrons (alpha particles have a charge of 2).
Imagine his surprise when a few alpha particles deflected at all angles,
even nearly straight backwards.
According to the plum pudding model there was nothing in the atom
massive enough to deflect the alpha particles. About this he said “. . . almost
as incredible as if you fired a 15-inch shell at a piece of tissue paper and it
came back and hit you.” He suggested the experimental data could only be
explained if the majority of the mass of an atom was concentrated in a small,
positively charged central nucleus. This experiment provided the evidence
needed to prove this nuclear model of the atom. In this experiment, you will
make observations similar to those of Professor Rutherford.
4573_PH_CHEM_Lab06_pp014-016 8/11/04 12:07 PM Page 15
Name ___________________________
Date ___________________
Class _____________
4. Point the cursor arrow to the detector (on the right). What detector is
used in this experiment?
5. Turn on the detector by clicking on the red/green light switch. What
does the signal in the middle of the screen represent?
What other signals do you see on the phosphor detection screen?
What do these signals represent?
Atomic Structure:
Rutherford’s Experiment
Click the Persist button (the dotted arrow) on the phosphor detector
screen. According to the plum pudding model, what is causing the
deflection of the alpha particles?
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Make an observation of the number of alpha particles hitting the
phosphor detection screen.
6. Now, you will make observations at different angles of deflection. Click
on the gray lab table window to bring it to the front. Grab the phosphor
detection screen by its base and move it to the spotlight in the top right
corner. The Persist button should still be on. Describe the number of hits
in this spotlight position as compared to the first detector position.
7. Move the detector to the top center spotlight position at a 90-degree
angle to the foil stand. Describe the number of hits in this spotlight
position as compared to the first detector position.
Atomic Structure: Rutherford’s Experiment
15
4573_PH_CHEM_Lab06_pp014-016 8/11/04 12:07 PM Page 16
Name ___________________________
Date ___________________
Class _____________
8. Move the detector to the top left spotlight position. Describe the number
of hits in this spotlight position as compared to the first detector
position.
What causes the alpha particles to deflect backwards?
How do these results disprove the plum pudding model? Keep in mind
that there are 1,000,000 alpha particles passing through the gold foil at
any given second.
Atomic Structure:
Rutherford’s Experiment
Are the gold atoms composed mostly of matter or empty space?
How does the Gold Foil Experiment show that almost all of the mass of
an atom is concentrated in a small positively charged central atom?
Further Investigation
1. Turn off the phosphor detection screen. Double-click the base of the
metal foil sample holder. It will move the holder to the stockroom
window. Click on the Stockroom to enter. Click on the metal sample box
on the top shelf. Click on Na to select sodium. Return to Lab.
2. Move the metal foil sample holder from the stockroom window back to
the center spotlight. Turn on the phosphor detection screen. Click Persist.
Observe the number of hits with sodium compared to the number of hits
with a gold sample. Why would Rutherford choose gold foil instead of
sodium foil? Explain.
16
Mollusks,
Atomic
Structure:
Arthropods,
Rutherford’s
and Echinoderms
Experiment
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Students often ask, “Why did Rutherford use gold foil?” The most common
response is that gold is soft and malleable and can be made into very thin
sheets of foil. There is another reason, which you can discover for yourself.
4573_PH_CHEM_Lab07_pp017-018 8/11/04 12:06 PM Page 17
Name ___________________________
Date ___________________
Class _____________
Lab 7: Atomic Emission Spectra
Purpose
To view atomic emission spectra and use a spectrometer to measure the
wavelength. The wavelength will be used to calculate frequency and
energy.
Procedure
Start Virtual ChemLab and select Atomic Emission Spectra from the list of
assignments.The lab will open in the Quantum laboratory.
The Spectrometer is on the right of the lab table. The emission spectra is
in the detector window in the upper right corner with a graph of the
Intensity vs (wavelength).
Analyze
2. Click on the Visible/Full switch to magnify only the visible spectrum. You
will see four peaks in the spectrum. If you drag your cursor over a peak,
it will identify the wavelength (in nm) in the x-coordinate field in the
bottom right corner of the window. Record the wavelength in the table
below for the four peaks in the hydrogen spectrum. (Round to whole
numbers.)
3. Each wavelength corresponds to another property of light called its
frequency. Use the wavelength value of each of the lines to calculate its
frequency given that n lc where c 2.998 1017 nm/s (2.998 108 m/s).
The energy (E) of a quantum of light an atom emits is related to its
frequency () by E h. Use the frequency value for each line and
h 6.63 1034 J.s to calculate its corresponding energy.
Wavelength (nm)
Frequency (1/s)
Atomic Emission
Spectra
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1. How many distinct lines do you see and what are their colors? Draw
what you see.
Energy (J)
Line #1 (left)
Line #2
Line #3
Line #4 (right)
Mollusks, Arthropods,
Atomic and
Emission
Echinoderms
Spectra
17
4573_PH_CHEM_Lab07_pp017-018 8/11/04 12:06 PM Page 18
Name ___________________________
Date ___________________
Class _____________
4. Now, investigate the emission spectra for a different element, helium.
Helium is the next element after hydrogen on the periodic table and
has two electrons. Do you think the emission spectra for an atom with
two electrons instead of one will be much different than hydrogen?
5. To exchange gas samples, turn off the Spectrometer with the On/Off
switch in the top right corner. Double-click on the Electric Field to place
it on the stockroom shelf. Double-click on the Gas (H2) sample tube to
place it on the stockroom shelf.
6. Click in the Stockroom. Click on the Gases samples on the top shelf. Click
on the cylinder labeled He to select helium as the gas and it will fill the
gas sample tube. If you point to the gas sample tube it should read He.
7. Return to lab. Drag the gas sample tube off the stockroom shelf. When
you select it, a white spotlight will appear indicating where you can
place the gas sample tube—place it there. Drag the Electric Field and
place it on the gas sample tube. Carefully click the button just above the
left zero on the volt meter and change the voltage to 300 V. Turn on the
Spectrometer. Click the Visible/Full switch to convert to only the visible
spectrum.
8. Draw the visible spectrum for helium. Is it different from hydrogen?
Atomic Emission
Spectra
Wavelength (nm)
Line (far right)
18
Mollusks,
Atomic
Emission
Arthropods,
Spectra
and Echinoderms
Frequency (1/s)
Energy (J)
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9. Determine the wavelength (in nm), the frequency (in 1/s) and the
energy (in J) for the peak on the far right.
4573_PH_CHEM_Lab08_pp019-021 8/11/04 12:06 PM Page 19
Name ___________________________
Date ___________________
Class _____________
Lab 8: Photoelectric Effect
Purpose
To duplicate photoelectric effect experiments.
Background
Though Albert Einstein is most famous for E mc2 and his work in
describing relativity in mechanics, his Nobel Prize was for understanding a
very simple experiment. It was long understood that if you directed light of
a certain wavelength at a piece of metal, it would emit electrons. In classical
theory, the energy of the light was thought to be based on its intensity and
not its frequency. However, the results of the photoelectric effect
contradicted classical theory. These inconsistencies led Einstein to suggest
that we need to think of light as being comprised of particles (photons) and
not just as waves.
Each wavelength corresponds to another property of light called
frequency. You will use the wavelength () value in the experiment to
calculate the frequency () given that n lc where c 2.998 1017 nm/s
(2.998 108 m/s). The energy (E) of a quantum of light an atom emits is
related to its frequency (n) by E h where h (Planck’s constant) 6.63 1034J-s.
Procedure
2. What source is used in this experiment and what does it do?
At what intensity is the laser set?
At what wavelength is the laser set?
Record the wavelength (in nm) in the data table. Calculate the frequency
(in 1/s) and the energy (in J) using the equations given in the
Background section of this lab. Determine the color of the light by
clicking on the Spectrum Chart (just behind the laser); the markers
indicate what color is represented by the wavelength selected.
Photoelectric Effect
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1. Start Virtual ChemLab and select Photoelectric Effect from the list of
assignments. The experiment opens in the Quantum laboratory.
Which metal foil is used in this experiment?
Mollusks, Arthropods,Photoelectric
and Echinoderms
Effect
19
4573_PH_CHEM_Lab08_pp019-021 8/11/04 12:06 PM Page 20
Name ___________________________
Date ___________________
Class _____________
What detector is used in this experiment and what does it measure?
Turn on the detector by clicking on the red/green light switch. What
does the signal on the phosphor screen indicate about the laser light
shining on the sodium foil?
3. Decrease the Intensity to 1 photon/second. How does the signal change?
Increase the Intensity to 1 kW. How does the signal change?
4. Change the Intensity back to 1 nW and increase the Wavelength to 600
nm. What do you observe? Record the wavelength in the data table.
Determine the maximum wavelength at which emission of electrons
occurs in the metal.
Which matters in the formation of photoelectrons: intensity or
wavelength?
wavelength (nm)
frequency (1/s)
energy (J)
400
Photoelectric Effect
600
450
20
Mollusks, Arthropods,
Photoelectric
Effect
and Echinoderms
light color
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
What is the difference between intensity and wavelength?
4573_PH_CHEM_Lab08_pp019-021 8/11/04 12:06 PM Page 21
Name ___________________________
Date ___________________
Class _____________
5. Click in the Stockroom. Click on the clipboard and select Photoelectric
Effect (2). Return to Lab. The intensity is set at 1 nW and the wavelength
at 400 nm. The detector used in this experiment is a bolometer. Turn on
the bolometer by clicking the red/green light switch. This instrument
measures the kinetic energy of electrons emitted from the metal foil. You
should see a green peak on the bolometer detection screen. The intensity
or height of the signal corresponds to the number of electrons being
emitted from the metal. The x-axis is the kinetic energy of the
photoemitted electrons. Zoom in on the peak by clicking and dragging
from half-way up the y-axis to the right past the peak and to the x-axis
(it will draw an orange rectangle).
6. Increase and decrease the Intensity, what do you observe?
Increase and decrease the Wavelength, what do you observe?
From this experiment, explain why violet light causes photoemission of
electrons but orange light does not.
Photoelectric Effect
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What is the maximum wavelength that ejects electrons from the sodium
metal?
Mollusks, Arthropods,Photoelectric
and Echinoderms
Effect
21
4573_PH_CHEM_Lab09_pp022-023 8/11/04 12:06 PM Page 22
Name ___________________________
Date ___________________
Class _____________
Lab 9: Diffraction Experiments
Diffraction
Experiments
Background
It has long been known that if you shine light through narrow slits that are
spaced at small intervals, the light will form a diffraction pattern. A
diffraction pattern is a series of light and dark patterns caused by wave
interference. The wave interference can be either constructive (light
patterns) or destructive (dark patterns). In this experiment, you will shine a
laser through a device with two slits where the spacing can be adjusted and
investigate the patterns that will be made at a distance from the slits.
Procedure
1. Start Virtual ChemLab and select Diffraction Experiments from the list of
assignments. The lab will open in the Quantum laboratory.
2. What source is used in this experiment and for what reason?
What is the wavelength of the Laser?
What is the spacing of the two slits on the two slit device?
Draw a picture of the pattern displayed on the video screen.
Change the Slit Spacing to 1 m. Observe the pattern displayed on the
video screen as you change the slit spacing from 1 m to 7 m by
one-micrometer increments. What can you state about the relationship
between slit spacing and diffraction pattern?
4. Increase the Wavelength of the Laser to 700 nm.
What affect does an increase in the wavelength have on the diffraction
pattern?
22
Diffraction Experiments
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3. Change the Intensity of the Laser from 1 nW to 1W.
Does the intensity of the light affect the diffraction pattern?
4573_PH_CHEM_Lab09_pp022-023 8/11/04 12:06 PM Page 23
Name ___________________________
Date ___________________
Class _____________
Diffraction
Experiments
5. Decrease the Intensity on the Laser to 1000 photons/second. Click on the
Persist button on the video camera to look at individual photons coming
through the slits. Observe for one minute. What observation can you
make about this pattern as compared to the pattern from the continuous
beam of photons?
Decrease the Intensity to 100 photons/second. Observe for another
minute after clicking Persist. At these lower intensities (1,000 and 100
photons/second), there is never a time when two photons go through
both slits at the same time. How can a single photon diffract?
From this experiment, what conclusions can you make about the nature
of light?
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
6. Click in the Stockroom. Click on the clipboard and select Two-Slit
Diffraction—Electrons. Return to Lab. What source is used in this
experiment?
Draw a picture of the diffraction pattern shown on the Phosphor Screen.
How does this diffraction pattern compare to the diffraction pattern for
light?
7. Decrease the Intensity to 10 electrons/second. The pattern now builds
one electron at a time. Click on the Persist button and observe for one
minute.
Has the diffraction pattern changed? Why or why not?
How can an electron diffract if there is only one?
Diffraction Experiments
23
4573_PH_CHEM_Lab10_pp024-026 8/11/04 12:05 PM Page 24
Name ___________________________
Date ___________________
Class _____________
Lab 10: Electronic State Energy Levels
Purpose
To understand the origins of Quantum Theory by using a spectrometer to
observe the emission spectrum of several gases.
Electronic State
Energy Levels
Background
Procedure
1. Start Virtual ChemLab and select Electronic State Energy Levels from the list
of assignments. The lab will open in the Quantum laboratory.
2. The lab table will be set up with four items. What is the detector on the
right?
What is the metal sample?
A heat source is used to heat the metal sample to high temperatures.
What is the temperature of the heat source?
3. Turn on the Spectrometer by clicking on the red/green light switch. Click
on the Visible/Full switch to change the view to the visible spectrum.
24
Electronic State Energy Levels
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
The classical picture of atoms would allow electrons to be at any energy
level. According to this classical model, when electrons are excited and
then fall back down to the ground state, they emit light at all wavelengths
and the emission spectrum would be continuous.
In the 1800s scientists found that when a sample of gas is excited by an
alternating electric current, it emits light only at certain discrete
wavelengths. This allowed for the development of spectroscopy, which is
used in the identification and analysis of elements and compounds. Even
though scientists found spectroscopy very useful, they could not explain
why the spectrum was not continuous. The explanation of this was left to
Niels Bohr, a Danish physicist. Bohr proposed that energy levels of
electrons are not continuous but quantized. The electrons only exist in
specific energy levels. Because of this quantization of energy, excited
electrons can only fall to discrete energy levels.
This assignment illustrates the measurements that helped Bohr develop
his quantum model, now known as Quantum Theory. It also illustrates
some practical uses for this science. Mercury vapor is used in fluorescent
lights and sodium vapor in street lighting.
You can separate the lines in the full region of an emission spectrum by
using an optical prism or a diffraction grating. A spectrometer is an
instrument designed to separate the emitted light into its component
wavelengths and plots the intensity of the light as a function of
wavelength.
4573_PH_CHEM_Lab10_pp024-026 8/11/04 12:05 PM Page 25
Name ___________________________
Date ___________________
Class _____________
Click on the Lab Book to open it. If any students in a previous class have
saved spectra, highlight and delete them. Click on the Record button (red
dot on the spectrometer window) to record this spectrum in the lab
book. Click just after the spectra file name and type tungsten metal.
What observations can you make about the emission spectrum for
heated tungsten metal?
Electronic State
Energy Levels
4. Turn the Spectrometer off with the On/Off switch. Click on the Stockroom.
Click the clipboard on the right. Click on the preset lab #9 Photoemission
– H2 and return to the lab by clicking on the Return to Lab arrow. Click
on the Visible/Full switch to change the view to the visible spectrum.
Record this spectrum in the Lab Book. Click just after the spectra file name
and type hydrogen gas. What observations can you make about the
emission spectrum for hydrogen gas?
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5. To exchange gas samples, turn off the Spectrometer. Double-click on the
Electric Field to place it on the stockroom shelf. Double-click on the Gas
(H2) sample tube to place it on the stockroom shelf.
6. Click in the Stockroom. Click on the Gases sample on the top shelf. Click
on the cylinder labeled Ne to select neon as the gas and it will fill the gas
sample tube. If you point to the gas sample tube it should read Ne.
7. Return to Lab. Drag the gas sample tube off the stockroom shelf. When
you select it, a white spotlight will appear indicating where you can
place the gas sample tube—place it there. Drag the Electric Field and
place it on the gas sample tube. Carefully click the button just above the
far left zero on the volt meter and change the voltage to 300 V. Turn on
the Spectrometer. Click the Visible/Full switch to convert to only the
visible spectrum. Record this spectrum in the lab book and identify this
link with the name of the element typed after the blue link.
8. Continue with this same process until you have completed the following
gas samples: H2, He, Ne, Na, and Hg. You should have five spectra
saved in the lab book in addition to tungsten metal. Record your
observations for each element. You can return to the lab book and click
on any of the spectra to view them again. Include in your observations a
comparison for each element to the spectrum for heated tungsten metal.
Electronic State Energy Levels
25
4573_PH_CHEM_Lab10_pp024-026 8/11/04 12:05 PM Page 26
Name ___________________________
Date ___________________
Class _____________
9. How do your observations of these gas emission spectra help confirm
Quantum Theory?
Application
1. Load the spectrum for heated tungsten metal. Tungsten metal is used in
incandescent light bulbs as the heated filament.
Electronic State
Energy Levels
2. Load the spectrum for mercury from the lab book into the spectrometer.
Examine the visible spectrum. Click the switch to change to full spectrum.
What differences do you see when changing between visible and full
spectrum for mercury?
Mercury vapor is used in the fluorescent light tubes that you see at school and
home. The emitted light is not very bright for just the mercury vapor, but
when scientists examined the full spectrum for mercury they saw what you
observed and recorded. There is an enormous emission in the ultraviolet
range (UV). This light is sometimes called black light. You may have seen it
with glow-in-the-dark displays.
3. Load the spectrum for sodium. What distinct feature do you see in the
sodium spectrum?
Astronomers are excited about cities changing from normal street lights to
sodium vapor street lights because astronomers can easily filter out the peak
at 589 nm and minimize light pollution.
26
Electronic State Energy Levels
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Scientists coat the inside of the glass tube of fluorescent light tubes with a
compound that will absorb UV and emit the energy as visible light with all
the colors of the rainbow. All colors together create white light which is why
fluorescent light tubes emit very white light.
4573_PH_CHEM_Lab11_pp027-029
8/12/04
2:01 PM
Page 27
Name ___________________________
Date ___________________
Class _____________
Lab 11: Pressure-Volume Relationship
for Gases
Purpose
Investigate the relationship between the pressure and volume of a gas.
Background
Robert Boyle studied the properties of gases in the 17th century. He noticed
that gases behave similarly to springs; when compressed or expanded, they
tend to ‘spring’ back to their original volume. You will make observations
similar to those of Robert Boyle.
The purpose of this experiment is to learn about the relationship
between pressure and volume of an ideal gas. In order to do this, you will
change the pressure or volume while the other is kept constant, and then
you will observe what happens.
Procedure
2. Note that the cylinder contains an ideal gas with a molecular weight of
4 g/mol. There is 0.3 mol of gas at a temperature of 298 K, a pressure of
1 atm, and a volume of 7.336 L. To the left of the pressure meter is a lever
that will decrease and increase the pressure as it is moved up or down;
the digit is changed depending on how far the lever is moved. Digits
may also be clicked directly to reach the desired number. You may want
to practice adjusting the lever so that you can decrease and increase the
pressure accurately. Make sure the moles, temperature, and pressure are
returned to their original values before proceeding.
Pressure-Volume
Relationship for Gases
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
1. Start Virtual ChemLab and select Pressure-Volume Relationship for Gases
from the list of assignments. The lab will open in the Gases laboratory.
3. Click on the Lab Book to open it. If data from a previous student appears,
delete it. Once back in the lab, click the Save button to start recording
your data. Increase the pressure from 1 atm to 10 atm one atmosphere at
a time. Click Stop. A blue data link will appear in the lab book. To keep
track of your data links, enter ‘Ideal Gas 1’ next to the link. Reset the lab.
4. Zoom Out by clicking the green arrow next to the Save button. Click
Return Tank on the gas cylinder. Click switch to change from Real Gases
to Ideal Gases. Choose Ideal 8 (Ideal 8 MW 222 g/mol). Click on the
balloon chamber to Zoom In. Set parameters to 0.3 mol of gas at a
temperature of 298 K and a pressure of 1 atm (the volume should be
7.336 L). Repeat the experiment with this gas labeling the data link as
‘Ideal Gas 8.’
Mollusks,
Pressure-Volume
Arthropods,
Relationship
and Echinoderms
for Gases
27
4573_PH_CHEM_Lab11_pp027-029 8/11/04 12:05 PM Page 28
Name ___________________________
Date ___________________
Class _____________
5. Zoom Out by clicking on the green arrow next to the Save button. Click on
the Stockroom and then on the Clipboard and select Balloon Experiment N2.
Set the parameters to 0.3 mol of gas at a temperature of 298 K, and a
pressure of 1 atm (the volume should be 7.334 L). You may have to click on
the Units button for some of the variables to change it to the correct unit.
Repeat the experiment with this gas labeling the data link ‘Real Gas N2.’
Analyze
1. Click the data link for Ideal Gas 1. Click the Select All button in the
Data Viewer window that will pop up. If you are using Windows use
CTRL-C, or on a Macintosh CMD-C to copy the data. Paste the data into
a spreadsheet and create a graph with volume on the x-axis and pressure
on the y-axis. Also create a graph for your data from Ideal Gas 8 and
Real Gas N2.
2. Based on your data, what relationship exists between the pressure and
volume of a gas (assuming a constant temperature)?
3. Look up a statement of Boyle’s Law in your textbook. Do your results
further prove this?)
4. Complete the tables from the data saved in your lab book. Use only a
sampling of the data for pressure at 1, 3, 6, and 9 atm.
Pressure-Volume
Relationship for Gases
Volume (L)
Pressure (atm)
PV Product (P V )
Ideal Gas 8 MW 222 g/mol
Volume (L)
28
Pressure (atm)
PV Product (P V )
Mollusks, Arthropods,
Pressure-Volume
Relationship
and Echinoderms
for Gases
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Ideal Gas 1 MW 4 g/mol
4573_PH_CHEM_Lab11_pp027-029 8/11/04 12:05 PM Page 29
Name ___________________________
Date ___________________
Class _____________
Real Gas N2
Volume (L)
Pressure (atm)
PV Product (P V )
5. What conclusions can you make about the PV product with Ideal Gas 1,
MW 4 g/mol?
How is the PV product affected using an ideal gas with a different
molecular weight (Ideal Gas 8)?
6. How are your results affected using a Real Gas (N2)?
Based on the results of this lab, develop a hypothesis to explain why
weather balloons are only partially filled before they are released into the
atmosphere. (These balloons can reach altitudes of 40,000 ft.)
Mollusks,
Pressure-Volume
Arthropods,
Relationship
and Echinoderms
for Gases
Pressure-Volume
Relationship for Gases
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Going Further
29
4573_PH_CHEM_Lab12_pp030-031 8/11/04 12:05 PM Page 30
Name ___________________________
Date ___________________
Class _____________
Lab 12: Temperature-Volume Relationship
for Gases
Purpose
Investigate the relationship between the temperature and volume of a gas.
Background
Charles’ Law was discovered by Joseph Louis Gay-Lussac in 1802, based
on unpublished work done by Jacques Charles in about 1787. Charles had
found that a number of gases expand to the same extent over the same 80
degree temperature interval. You will be observing properties similar to
those that Charles studied.
The purpose of this experiment is to learn about the relationship
between temperature and volume of an ideal gas. You will do this by
keeping all variables constant except temperature and volume to observe
what happens.
According to the kinetic theory of gases, the average kinetic energy of
the gas increases with the temperature. When gas is in a rigid container, the
pressure (exerted by the gas on the walls of the container) increases as the
temperature increases.
Procedure
1. Start Virtual ChemLab and select Temperature-Volume Relationship for Gases
from the list of assignments. The lab will open in the Gases laboratory.
Temperature-Volume
Relationship for Gases
3. Click on the Lab Book to open it. If data from a previous student appears,
delete it. Once back in the lab, click the Save button to start recording
your data. Increase the temperature from 100°C to 1000°C 100 degrees at
a time. Click Stop. A blue data link will appear in the lab book. To help
keep track of your data links, enter ‘Ideal Gas 1’ next to the link.
Analyze
1. Click the data link for Ideal Gas 1. Click the Select All button in the Data
Viewer window. If you are using Windows, use CTRL-C or on a Macintosh
CMD-C to copy the data. Paste your data into a spreadsheet and create a
graph with volume on the x-axis and temperature on the y-axis.
30
Mollusks, Arthropods,Relationship
Temperature-Volume
and Echinoderms
for Gases
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
2. Note that you are using an Ideal gas with a molecular weight of 4
g/mol. There is 0.05 mol of gas at a temperature of 100°C, a pressure of 1
atm, and a volume of 1.531 L. To the left of the temperature meter is a
lever that will decrease and increase the temperature as it is moved up
or down; the digit is changed depending on how far the lever is moved.
Digits may also be clicked directly to type in the desired number, or they
can be rounded by clicking on the R button. You may want to practice
adjusting the lever so that you can decrease and increase the
temperature accurately. Make sure the moles, temperature, and pressure
are returned to their original values before proceeding.
4573_PH_CHEM_Lab12_pp030-031 8/11/04 12:05 PM Page 31
Name ___________________________
Date ___________________
Class _____________
2. Based on your data, what relationship exists between the pressure and
volume of a gas (assuming constant temperature)?
3. Look up a statement of Charles’ Law in your textbook. Do your results
further prove this?
4. Using the spreadsheet, fit the data to a curve (linear fit). The lowest
possible temperature is reached when an Ideal Gas has zero volume.
This temperature is the y-intercept for the plotted line. What is this
temperature?
6. What lowest temperature did you find for the Real Gas (N2)?
Going Further
Interpret the results of this lab in terms of the kinetic theory of matter as it
applies to gases.
Temperature-Volume
Relationship for Gases
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
5. Zoom Out by clicking on the green arrow next to the Save button. Click
on the Stockroom and then on the Clipboard and select Balloon Experiment
N2. Set the parameters to 0.05 mol of gas at a temperature of 100°C, and
a pressure of 1 atm (the volume should be 1.531 L). You may have to
change the units for some of the variables. Repeat the experiment that
was performed on the ideal gas by increasing the temperature from
100°C to 900°C by increments of 100°C saving the data to the lab book
and label the link as ‘Real Gas N2.’ Plot the data and fit it to a linear
curve.
Temperature-Volume
Mollusks, Arthropods,
Relationship
and Echinoderms
for Gases
31
4573_PH_CHEM_Lab13_pp032-033
8/12/04
2:01 PM
Page 32
Name ___________________________
Date ___________________
Class _____________
Lab 13: Derivation of the Ideal Gas Law
Derivation of Ideal
Gas Law
Purpose
Derive the Ideal Gas Law from experimental procedures and determine the
value of the Universal Gas Constant (R).
Background
An ideal gas is a hypothetical gas whose pressure, volume, and
temperature follow the relationship PV nRT. No ideal gases actually
exist, although all real gases behave similarly to ideal gases near room
temperature and pressure. All gases can be described to some extent using
the Ideal Gas Law, which is important in our understanding of how all
gases behave. You will be deriving the Ideal Gas Law.
The state of any gas can be described using the four variables: pressure
(P), volume (V), temperature (T), and the number of moles of gas (n). Each
experiment in the Gases Simulation allows three of these variables (the
independent variables) to be manipulated or changed and then shows the
effect on the remaining variable (the dependent variable).
Procedure
1. Start Virtual ChemLab and select Derivation of the Ideal Gas Law from the
list of assignments. The lab will open in the Gases laboratory.
3. Use this same experiment to describe the relationship between
temperature (T) and volume, by increasing and decreasing the
temperature. What can you conclude about the effect of temperature on
volume? Write a mathematical relationship.
4. Use this same experiment to describe the relationship between moles of
gas and volume, by increasing and decreasing the number of moles (n).
What can you conclude about the effect of moles on volume? Write a
mathematical relationship.
32
Mollusks, Arthropods,
Derivation
of Ideal Gasand
LawEchinoderms
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
2. Use the balloon experiment to describe the relationship between
pressure (P) and volume (V). Increase and decrease the pressure using
the lever to the left of the pressure to determine the effect on volume.
What can you conclude about the effect of pressure on volume? Write a
mathematical relationship.
4573_PH_CHEM_Lab13_pp032-033 8/11/04 12:04 PM Page 33
Name ___________________________
Date ___________________
Class _____________
Derivation of Ideal
Gas Law
5. Since volume is proportional to inverse pressure, temperature and
moles we can combine these three proportions into one proportion
showing V proportional to 1/P, T, and n. Write one combined
proportion to show the relationship of volume to pressure, temperature
and moles.
6. This proportional relationship can be converted into a mathematical
equation by inserting a proportionality constant (R) into the numerator
on the right side. Write this mathematical equation and rearrange with
P on the left side with V.
7. This equation is known as the Ideal Gas Law. Using data for volume,
temperature, pressure and moles from one gas apparatus experiment,
L # atm
calculate the value for R with the units K
# mol . (Show all work and
round to three significant digits).
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
8. Using the relationship between atmospheres and
mm Hg of 1 atm 760 mm Hg, calculate the value for R with the units
L # atm
K # mol. (Show all work and round to three significant digits).
9. Using the relationship between atmospheres and
L # atm
kPa of 1 atm 101.3 kPa, calculate the value for R with the units K
# mol.
(Show all work and round to three significant digits).
Mollusks, Arthropods,
Derivationand
of Ideal
Echinoderms
Gas Law
33
4573_PH_CHEM_Lab14_pp034-036 8/11/04 12:04 PM Page 34
Name ___________________________
Date ___________________
Class _____________
Lab 14: Ideal vs Real Gases
Purpose
Investigate how temperature and pressure changes affect ideal and real
gases.
Background
In the Ideal Gas Law lab previously completed, you learned how to derive
the Ideal Gas Law (PV nRT) from observations about the relationships
between volume, temperature, pressure and moles. You calculated the
value for the Universal Gas Constant (R) for an ideal gas. In this
experiment you will also calculate the Universal Gas Constant (R), but with
both ideal and real gases and at high and low temperatures and pressures.
Ideal vs Real Gases
Procedure
1. Start Virtual ChemLab and select Ideal vs Real Gases from the list of
assignments. The lab will open in the Gases laboratory with Ideal Gas 1.
2. Click on the Units buttons to change the units to L or mL for volume,
atm for pressure, and K for temperature.
The small R button in the upper left corner rounds the number. Clicking
several times will round from ones to tens to hundreds. The green arrow
to the left of the Save button will Zoom Out. Clicking Return Tank on the
gas cylinder will return the tank to the rack and allow you to select a
different gas. Clicking the gas chamber will Zoom In to allow you to
change parameters.
Be careful not to make the balloon so large that it bursts. If it does, click
the red Reset button in the top right and then reset your units and values
for each parameter.
Remember that volume must be in L. If mL appears, you must convert
to L in your calculations.
34
Mollusks,
Ideal
vs Real
Arthropods,
Gases
and Echinoderms
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
To change the value of pressure, temperature or moles, the lever to the
left of each number can be used. The value will decrease and increase as
the lever is moved up or down; the digit is changed depending on how
far the lever is moved. Digits may also be clicked directly to reach the
desired number. Clicking to the left of the farthest left digit will add the
next place; for example, if you have 1.7 atm you can click left of the 1
and enter 2 to make it 21.7 atm or click left of the 2 and enter 5 to make it
521.7 atm.
4573_PH_CHEM_Lab14_pp034-036 8/11/04 12:04 PM Page 35
Name ___________________________
Date ___________________
Class _____________
3. Complete the Data Table for the following gases and conditions (all with
0.1 mol):
a. Ideal gas at low T 10 K, high T 1000 K, low P 1 atm, high P 15 atm
b. Methane gas (CH4) at low T 160 K, high T 400 K, low P 1 atm,
high P 15 atm
c. Carbon dioxide gas (CO2) at low T 250 K, high T 1000 K, low P 1 atm, high P 15 atm
Gas
V (L)
P (atm)
T (K)
n (mol)
Ideal, low T, low P
Ideal, low T, high P
Ideal, high T, low P
Ideal vs Real Gases
Ideal, high T, high P
CH4, low T, low P
CH4, low T, high P
CH4, high T, low P
CH4, high T, high P
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CO2, low T, low P
CO2, low T, high P
CO2, high T, low P
CO2, high T, high P
Analyze
1. If PV nRT then R PV/nT. Complete the table for each experiment
above. Use four significant digits.
Mollusks, Arthropods,Ideal
and vs
Echinoderms
Real Gases
35
4573_PH_CHEM_Lab14_pp034-036 8/11/04 12:04 PM Page 36
Name ___________________________
Gas
Date ___________________
Class _____________
Calculated R (1-atm/K-mol)
Ideal, low T, low P
Ideal, low T, high P
Ideal, high T, low P
Ideal, high T, high P
CH4, low T, low P
CH4, low T, high P
CH4, high T, low P
Ideal vs Real Gases
CH4, high T, high P
CO2, low T, low P
CO2, low T, high P
CO2, high T, low P
CO2, high T, high P
36
Ideal vs Real Gases
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
2. Which gases and conditions show significant deviation from the ideal
value of R? Explain.
4573_PH_CHEM_Lab15_pp037-038 8/11/04 12:04 PM Page 37
Name ___________________________
Date ___________________
Class _____________
Lab 15: Investigation of Gas Pressure
and Mass
Purpose
Investigate the relationship between the internal pressure of a gas and the
applied external pressure by placing weights on a frictionless, massless
piston.
Background
An understanding of pressure is an integral part of our understanding of
the behavior of gases. Pressure is defined as the force per unit area exerted
by a gas or other medium. The pressure of a gas is affected by many
variables, such as temperature, external pressure, volume, number of moles
of a gas, and other factors. This experiment will help you to become more
familiar with pressure.
Procedure
2. To investigate the relationship between mass added to the piston
to apply an external pressure, note that in this experiment
Pint Pmass Pext, where Pint is the internal pressure or the pressure
of the gas in the cylinder, Pmass is the pressure being exerted on the
gas by adding weights to the piston, and Pext is the pressure being
exerted on the piston by the gas in the chamber.
3. Click the green Piston button to move the piston into position. Record
the force (in tons) and the internal pressure (in psi) in the Data Table.
Investigation of Gas
Pressure and Mass
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
1. Start Virtual ChemLab and select Investigation of Gas Pressure and Mass
from the list of assignments. The lab will open in the Gases laboratory.
4. Click on the tenths place for force and add 0.5 tons of force to the piston.
Record the force and internal pressure in the table. Repeat this for
2.5 tons (the weight of a small car).
force (tons)
external pressure
(psi)
calculated internal
pressure (psi)
internal pressure
from meter (psi)
0
.5
2.5
Mollusks,
Investigation
Arthropods,
of Gas Pressure
and Echinoderms
and Mass
37
4573_PH_CHEM_Lab15_pp037-038 8/11/04 12:04 PM Page 38
Name ___________________________
Date ___________________
Class _____________
Analyze
1. You must now calculate the pressure being exerted by the 0.5 tons or,
Pmass. First, convert tons to psi (pounds per square inch).
How many pounds is 0.5 tons?
The diameter of the piston is 15 cm. What is the radius (in cm)?
1 inch 2.54 cm. What is the radius of the piston in inches?
The area of the circular piston is found by A r2. What is the area of
the piston in square inches (in2)?
The pressure exerted on the piston by the added mass in pounds per
square inch (psi) can be determined by dividing the mass in pounds by
the area in square inches. What is the pressure exerted by the added
mass in psi?
2. Predict the internal pressure (in psi) when 2.5 tons are added.
How does your calculated answer compare to the internal pressure
meter when you add 2.5 tons of mass? Record your data in the table.
38
Mollusks, Arthropods,
Investigation
of Gas Pressure
and Echinoderms
and Mass
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Investigation of Gas
Pressure and Mass
The internal pressure is the sum of the external pressure and the added
mass. What is the calculated internal pressure? Compare your calculated
answer to the internal pressure meter answer. How do they compare?
4573_PH_CHEM_Lab16_pp039-041 8/11/04 12:03 PM Page 39
Name ___________________________
Date ___________________
Class _____________
Lab 16: The Specific Heat of a Metal
Purpose
Determine the specific heat of a metal using a calorimeter.
Background
On a sunny day, the water in a swimming pool may warm up a degree or
two while the concrete around the pool may become too hot to walk on
with bare feet. This may seem strange since the water and concrete are
being heated by the same source—the sun. This evidence suggests it takes
more heat to raise the temperature of some substances than others, which is
true. The amount of heat required to raise the temperature of 1 g of a
substance by 1 degree K is called the specific heat capacity, or specific heat, of
that substance. Water, for instance, has a specific heat of 4.18 J/K # g. This
value is high in comparison with the specific heats for other materials, such
as concrete or metals. In this experiment, you will use a simple calorimeter
and your knowledge of the specific heat of water to determine the specific
heat of several metals.
Procedure
2. Click on the Lab Book to open it. Record the mass of Pb on the balance. If
it is too small to read click on the Balance area to zoom in, record the
mass of Pb in the Data Table, and return to the laboratory.
3. Pick up the Pb sample from the balance pan and place the sample in the
oven. Click the oven door to close. The oven is set to heat to 200°C.
4. The calorimeter has been filled with 100 mL water. The density of water
at 25°C is 0.998 g/mL. Use the density of the water to determine the
mass from the volume and record the volume and mass in the Data
Table.
Make certain the stirrer is On (you should be able to see the shaft
rotating). Click the thermometer window to bring it to the front and
click Save to begin recording data. Allow 20–30 seconds to obtain a
baseline temperature of the water.
5. Click on the Oven to open it. Drag the hot lead sample from the oven
until it snaps into place above the calorimeter and drop it in. Click the
thermometer and graph windows to bring them to the front again and
observe the change in temperature in the graph window until it reaches
a constant value and then wait an additional 20–30 seconds. Click Stop in
the temperature window. You can click on the Accelerate button on the
clock to accelerate the time in the laboratory. A blue data link will appear
in the lab book. Click the blue data link and record in the Data Table the
temperature before adding the Pb and the highest temperature after
adding the Pb.
Mollusks, Arthropods,
The Specific
and
Heat
Echinoderms
of a Metal
The Specific Heat
of a Metal
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
1. Start Virtual ChemLab and select The Specific Heat of a Metal from the list
of assignments. The lab will open in the Calorimetry laboratory.
39
4573_PH_CHEM_Lab16_pp039-041 8/11/04 12:03 PM Page 40
Name ___________________________
Date ___________________
Class _____________
6. Repeat the experiment with a metal sample of your choosing. Click the
red disposal bucket to clear the lab. Click on the Stockroom to enter.
Double-click the Dewar calorimeter to move it to the Stockroom counter.
Click the metal sample cabinet. Click a drawer (the samples are
alphabetically arranged), and select a sample by double-clicking and
zoom out. Double-click on the petri dish with the selected sample to
move it to the Stockroom counter. Return to the laboratory.
7. Move the petri dish with metal sample to the spotlight next to the
balance. Click on the Balance area to zoom and make sure the balance
has been tared. Move the metal sample to the balance pan and record the
mass in the table. Return to the laboratory.
8. Double-click the calorimeter to move it into position in the laboratory.
Click the oven to open the door. Move the metal sample from the
balance pan to the oven and click to close the oven door. Click above the
tens place several times on the front of the oven to change the
temperature to 200°C. Fill the 100 mL graduated cylinder with water by
holding it under the tap until it returns to the counter and then pour it
into the calorimeter. Turn on the thermometer. Click on the Graph and
Save buttons. Move your metal sample from the oven to the calorimeter.
Follow the procedures used with Pb to obtain the equilibrium
temperature. Record your observations in the table.
Pb
your choice
volume of water (mL)
mass of water (g)
initial temperature of water (°C)
initial temperature of metal (°C)
max temp of water metal (°C)
Analysis and Conclusions
The Specific Heat
of a Metal
1. Determine the changes in temperature of the water ( ¢ Twater).
2. Calculate the heat (q) gained by the water using the following equation:
qwater mwater # ¢Twater # Cwater, given Cwater 4.184 J/(g°C)
40
Mollusks,
The
Specific
Arthropods,
Heat of a Metal
and Echinoderms
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mass of metal (g)
4573_PH_CHEM_Lab16_pp039-041 8/11/04 12:03 PM Page 41
Name ___________________________
Date ___________________
Class _____________
3. Determine the changes in temperature of the Pb ( ¢ TPb).
4. Remembering that the heat gained by the water is equal to the heat lost
by the metal, calculate the specific heat of lead.
qmetal
qwater qmetal mPb # ¢TPb # CPb and CPb (mmetal)(¢Tmetal)
5. Calculate the percent error in the specific heat value that you
determined experimentally. Use the accepted value given by your
teacher.
0 your answer accepted answer 0
% Error 100
accepted answer
6. Repeat the calculation of specific heat capacity for your choice of metals
and calculate the percent error. Use the accepted value given by your
teacher.
8. The calorimeter would probably absorb some of the heat. If we consider
this source of error we can correct for it by modifying the specific heat of
water to include the heat absorbed by the calorimeter. The corrected
J
specific heat of water for the calorimeter is 5.224 k # g. Calculate the
most accurate specific heat for lead and the metal of your choosing.
What is the percent error for each using your new calculation?
The Specific Heat
of a Metal
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7. What assumptions have been made that might affect your answers?
The Specific Heat of a Metal
41
4573_PH_CHEM_Lab17_pp042-043 8/11/04 12:03 PM Page 42
Name ___________________________
Date ___________________
Class _____________
Lab 17: Heat of Fusion of Water
Purpose
Heat of Fusion
of Water
To measure the heat of fusion of water using a calorimeter.
Procedure
1. Start Virtual ChemLab and select Heat of Fusion of Water from the list of
assignments. The lab will open in the Calorimetry laboratory with a
beaker of ice on the balance and a coffee cup calorimeter on the lab
bench.
2. Click on the Lab Book to open it. Record the mass of the ice on the
balance. If it is too small to read, click on the Balance area to zoom in and
record the mass of ice in the Data Table.
3. 100 mL of water is already in the coffee cup. Use the density of water at
25°C (0.998 g/mL) to determine the mass from the volume and record in
the Data Table. Make certain the stirrer is On (you should be able to see
the shaft rotating). Click the thermometer window to bring it to the front
and click Save to begin recording data. Allow 20–30 seconds to obtain a
baseline temperature of the water.
5. If you want to repeat the experiment, click on the red disposal bucket to
clear the lab, click on the Stockroom, click on the clipboard and select
Preset Experiment 3, Heat of Fusion of Water.
volume of water in calorimeter (mL)
mass of water in calorimeter (g)
mass of ice (g)
initial temperature (°C)
final temperature (°C)
42
Mollusks,
Heat
of Fusion
Arthropods,
of Waterand Echinoderms
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4. Drag the beaker from the balance area until it snaps into place above the
coffee cup and pour the ice into the calorimeter. Click the thermometer
and graph windows to bring them to the front again and observe the
change in temperature in the graph window until it reaches a constant
value. Click Stop in the temperature window. Click on the Accelerate
button on the clock to accelerate the time in the laboratory. A blue data
link will appear in the lab book. Click the blue data link and record in
the Data Table the temperature before adding the ice and the lowest
temperature after adding ice.
4573_PH_CHEM_Lab17_pp042-043 8/11/04 12:03 PM Page 43
Name ___________________________
Date ___________________
Class _____________
Analysis and Conclusion
1. Calculate ¢ T for the water by ¢ T |Tf – Ti|.
Heat of Fusion
of Water
2. Calculate the heat (q) transferred from the water to the ice by q mC ¢ T
where the heat capacity (C) for water is 4.18 J/g°C and the mass is for
the water in the calorimeter. Convert to kJ/mol.
3. Convert the mass of ice to moles.
4. Calculate ¢ Hfus of ice (kJ/mol) by dividing the heat transferred from the
water by the moles of ice melted.
5. Compare your experimental value of ¢ Hfus of ice with the accepted
value of 6.01 kJ/mol and calculate the % error as:
% Error 0 your answer accepted answer 0
100
accepted answer
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6. What possible sources of error could there be in this laboratory
procedure?
Mollusks, Arthropods,
Heat of
and
Fusion
Echinoderms
of Water
43
4573_PH_CHEM_Lab18_pp044-046 8/11/04 12:02 PM Page 44
Name ___________________________
Date ___________________
Class _____________
Lab 18: Heats of Reaction
Purpose
Measure the heats of reaction for three related exothermic reactions and to
verify Hess’s law.
Background
Energy changes occur in all chemical reactions; energy is either absorbed or
released. If energy is released in the form of heat, the reaction is called
exothermic. If energy is absorbed, the reaction is called endothermic. In this
experiment, you will measure the amount of heat released in these three
related exothermic reactions:
NaOH (s) S Na (aq) OH (aq) ¢ H1
Heats of Reaction
NaOH (s) H (aq) Cl (aq) S H2O Na (aq) Cl (aq) ¢ H2
Na (aq) OH (aq) H (aq) Cl (aq) S H2O Na (aq) Cl(aq) ¢ H3
After determining the heats of reaction, you will analyze your data and
verify the additive nature of heats of reaction.
Procedure
Start Virtual ChemLab and select Heats of Reaction from the list of
assignments. The lab will open in the Calorimetry laboratory.
Reaction 1
2. Drag the weigh paper with the sample to the calorimeter until it snaps
into place and pour the sample into the calorimeter. Observe the
change in temperature until it reaches a maximum and then record data
for an additional 20–30 seconds. Click Stop. Click on the Accelerate
button on the clock to accelerate the time in the laboratory. A blue data
link will appear in the Lab Book. Click the data link and record the
initial and final water temperatures in the Data Table. If you need to
repeat this part of the experiment, enter the Stockroom and select
Preset Experiment #6 on the clipboard.
44
Mollusks,
Heats
of Reaction
Arthropods, and Echinoderms
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1. There will be a bottle of NaOH near the balance (move the plot
window to see it). A weigh paper will be on the balance with
approximately 4 g NaOH on the paper. The calorimeter will be on the
lab bench and filled with 200 mL water. Click the Lab Book to open it.
Make certain the stirrer is On (you should be able to see the shaft
rotating). In the thermometer window click Save to begin recording
data. Allow 20–30 seconds to obtain a baseline temperature of the
water.
4573_PH_CHEM_Lab18_pp044-046 8/11/04 12:02 PM Page 45
Name ___________________________
Date ___________________
Class _____________
Reaction 2
1. Click the red disposal bucket to clear the lab. Click on the Stockroom to
enter. Click on the clipboard and select Preset Experiment #5. Return to
the laboratory.
2. There will be a bottle of NaOH near the balance. A weigh paper will be
on the balance with approximately 4 g NaOH on the paper. The
calorimeter will be on the lab bench and filled with 100 mL water, and
there will be a beaker containing 100 mL of 1.000 M HCl on the lab
bench. In the thermometer window click Save to begin recording data.
Allow 20–30 seconds to obtain a baseline temperature of the water.
Heats of Reaction
3. Make sure the beaker of HCl is visible and drag it to the calorimeter
and pour it into the calorimeter. The HCl and the water are at the same
temperature so there should be no temperature change. Now drag the
weigh paper with the NaOH to the calorimeter until it snaps into place
and pour the sample into the calorimeter. It is important that the HCl
be added first and the NaOH added second. Observe the change in
temperature until it reaches a maximum and then record data for an
additional 20–30 seconds. Record the temperature before adding the
HCl and after adding the NaOH.
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Reaction 3
1. Click the red disposal bucket to clear the lab. Click on the Stockroom to
enter. Click on the clipboard and select Preset Experiment #4. Return to
the laboratory.
2. In the thermometer window click Save to begin recording data. Allow
20–30 seconds to obtain a baseline temperature of the water. Pour the
first beaker containing the HCl into the calorimeter and then pour the
second beaker containing the NaOH into the calorimeter. Observe the
change in temperature until it reaches a maximum and then record data
for an additional 20–30 seconds. Record the initial and final
temperatures.
Parameter
Reaction 1
Reaction 2
Reaction 3
Mass NaOH
initial temperature (°C)
final temperature (°C)
Analysis and Conclusions
1. Determine the change in temperature, ¢ T, for each reaction. Record
your results in the table.
Mollusks, Arthropods, and
Heats
Echinoderms
of Reaction
45
4573_PH_CHEM_Lab18_pp044-046
8/12/04
2:00 PM
Page 46
Name ___________________________
Date ___________________
Class _____________
2. Calculate the mass of the reaction mixture in each reaction. (To do this,
first determine the total volume of the solution. Then calculate the mass
of the solution, based on the assumption that the added solid does not
change the volume and that the density of the solution is the same as
that of pure water, 1.0 g/mL.) Remember to add the mass of the solid.
Record your results in the table.
3. Calculate the total heat released in each reaction, assuming that the
specific heat capacity of the solution is the same as that of pure water,
4.184J
K#g.
Record the result in the table.
Heats of Reaction
4. Calculate the number of moles of NaOH used in reactions 1 and 2
where n = m/MW. Record the results in the table.
5. Calculate the number of moles of NaOH used in reaction 3 by
multiplying the volume of NaOH times the molarity (1.000 mol/L).
Record the results in the table.
6. Calculate the energy released in kJ/mol of NaOH for each reaction and
record the results in the table.
Mass of
Rxn Mixture
DT
Total Heat
Released
mol NaOH
Heat Released
per mol NaOH
1
2
3
7. Show that the equations for reactions 1 and 3, which are given in the
Background section, add to give the equation for reaction 2. Include the
energy released per mole of NaOH in each equation.
46
Mollusks,
Heats
of Reaction
Arthropods, and Echinoderms
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
#
Rxn
4573_PH_CHEM_Lab19_pp047-049 8/11/04 12:02 PM Page 47
Name ___________________________
Date ___________________
Class _____________
Lab 19: Heat of Combustion
Purpose
Measure the heat of combustion of sugar.
Background
The heat of combustion is the heat of reaction for the complete burning of
one mole of a substance. Calorimetry experiments such as the
determination of the heat of combustion ( ¢ Hcomb) can be performed at
constant volume using a device called a bomb calorimeter.
In this assignment you will calculate the heat of combustion of table
sugar (sucrose, C12H22O11). The calorimeter must also be calibrated by first
combusting benzoic acid.
Procedure
1. Start Virtual ChemLab and select Heat of Combustion from the list of
assignments. The lab will open in the Calorimetry laboratory with the
bomb calorimeter out, disassembled, and a sample of benzoic acid in the
calorimeter cup on the balance. The balance has already been tared.
Calibration of the calorimeter
3. Record the mass of the benzoic acid sample from the balance. If you
cannot read it, click on the Balance area to zoom in, record the mass, and
return to the laboratory.
4. Double-click in this order to assemble the calorimeter: (1) the cup on the
balance pan, (2) the bomb head, (3) the screw cap, and (4) the bomb.
Click the calorimeter lid to close. Combustion experiments can take a
considerable length of time. Click the clock on the wall labeled Accelerate
to accelerate the laboratory time.
Heat of Combustion
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2. Click on the Lab Book to open it. Highlight and delete any data links left
by a previous student.
5. Click the Bomb control panel and the Plot window to bring them to the
front. Click on the Save button to save data to the lab book. Allow the
graph to proceed for 20–30 seconds to establish a baseline temperature.
6. Click Ignite and observe the graph. When the temperature has leveled
off (up to 5 minutes of laboratory time), click Stop. A blue data link will
appear in the lab book. Click the blue data link to view the collected
data. Record in the Data Table the temperature before and after ignition
of the benzoic acid sample.
Combustion of sugar
7. Click the red disposal bucket to clear the lab. Click on the Stockroom to
enter. Click on the clipboard and select Preset Experiment #13. Return to
the laboratory.
Mollusks, Arthropods,
Heat
andofEchinoderms
Combustion
47
4573_PH_CHEM_Lab19_pp047-049 8/11/04 12:02 PM Page 48
Name ___________________________
Date ___________________
Class _____________
8. Repeat steps 4–7 for sucrose. Record your observations in the table.
benzoic acid (C7H6O2)
sucrose (C12H22O11)
mass of sample (g)
initial temperature (°C)
final temperature (°C)
Calibration of calorimeter
1. Calculate ¢ T for the water in the benzoic acid combustion by ¢ T |Tf – Ti|.
Calculate the moles of benzoic acid (MW 122.13 g/mol). n mass
sample/molecular weight
2. ¢ Hcomb for benzoic acid can be calculated by ¢ H (Csystem ¢ T)/n ,
where n is the moles of benzoic acid in the sample and Csystem is the heat
capacity of the calorimetric system. If the accepted value for the heat of
combustion for benzoic acid is 3226 kJ/mol, calculate the heat capacity
(Csystem) of the calorimetric system.
Heat of Combustion
1. Calculate ¢ T for the water by ¢ T |Tf – Ti|.
2. Calculate the moles of sucrose in the sample (MWsucrose 342.3 g/mol).
3. ¢ Hcomb for sucrose can be calculated by ¢Hcomb (Csystem ¢T)>n, where
n is the moles of benzoic acid in the sample and Csystem is the heat
capacity of the calorimetric system. Using the value you calculated for
Csystem, calculate the heat of combustion for sucrose.
4. If the accepted value for the heat of combustion for sugar is 5639
kJ/mol, calculate the percent error.
0 your answer accepted answer 0
%Error 100
accepted answer
48
Mollusks,
Heat
of Combustion
Arthropods, and Echinoderms
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Heat of combustion of sucrose
4573_PH_CHEM_Lab20_pp049-050 8/11/04 12:02 PM Page 49
Name ___________________________
Date ___________________
Class _____________
Lab 20: Enthalpy and Entropy
Purpose
Observe and measure energy changes during the formation of a solution
and to describe and explain those changes in terms of entropy and enthalpy.
Procedure
1. Start Virtual ChemLab and select Enthalpy and Entropy from the list of
assignments. The lab will open in the Calorimetry laboratory.
2. There will be a bottle of sodium chloride (NaCl) on the lab bench. A
weigh paper will be on the balance with approximately 2 g of NaCl on
the paper.
4. Drag the weigh paper with the sample to the calorimeter until it snaps in
place and pour the sample in the calorimeter. Observe the change in
temperature until it reaches a maximum and then record data for an
additional 20–30 seconds. Click Stop. Click on the Accelerate button on
the clock to accelerate the time in the laboratory.) A blue data link will
appear in the Lab book. Click the data link and record the initial and
final water temperatures in the Data Table.
5. Click the red disposal bucket to clear the lab. Click on the Stockroom to
enter. Click on the clipboard and select Preset Experiment #7 and repeat
the experiment with NaNO3. Record the initial and final temperatures in
the Data Table.
6. Click the red disposal bucket to clear the lab. Click on the Stockroom to
enter. Click the clipboard and select Preset Experiment #8 and repeat the
experiment with NaCH3COO (NaAc). Record the initial and final
temperatures in the Table.
Mixture
T1
T2
¢T
NaCl (s) H2O (l)
NaNO3 (s) H2O (l)
Enthalpy and Entropy
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3. The calorimeter will be on the lab bench and filled with 100 mL water.
Click the Lab Book to open it. Make certain the stirrer is On (you should
be able to see the shaft rotating). In the thermometer window click Save
to begin recording data. Allow 20–30 seconds to obtain a baseline
temperature of the water.
NaCH3COO H2O (l)
Mollusks, Arthropods,
Enthalpy
and Echinoderms
and Entropy
49
4573_PH_CHEM_Lab20_pp049-050 8/11/04 12:02 PM Page 50
Name ___________________________
Date ___________________
Class _____________
Analyze
Use your experimental data to answer the following questions in or below
your data table.
1. Calculate ¢ T for each mixture. ¢ T T2 – T1
2. An exothermic process gives off heat (warms up). An endothermic
process absorbs heat (cools off). Which solutions are endothermic and
which are exothermic? What is the sign of the change in enthalpy in each
case?
3. Which solution(s) had little or no change in temperature?
4. When sodium chloride dissolves in water, the ions dissociate.
NaCl (s) S Na (aq) Cl (aq)
Write ionic equations, similar to the one above, that describe how
NaNO3 and NaCH3COO each dissociate as they dissolve in water.
Include heat as a reactant or product in each equation.
5. What is the sign of the Gibbs free energy ( ¢ G) for each process?
Enthalpy and Entropy
7. If the sign for ¢ G is negative (spontaneous process) and the sign for ¢ S
is positive (more disorder) for both dissolving processes, how could one
be endothermic (positive ¢ H) and one be exothermic (negative ¢ H)? Is
there more to consider than just the dissolving process?
50
Mollusks,and
Enthalpy
Arthropods,
Entropy and Echinoderms
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6. Consider the Gibbs-Hemholtz equation, ¢ G ¢ H T ¢ S. For each
dissolving process, substitute the sign of ¢ G and ¢ H into the equation
and predict the sign for the entropy ( ¢ S). Does the sign for entropy seem
logical? Explain
4573_PH_CHEM_Lab21_pp051-052 8/11/04 12:01 PM Page 51
Name ___________________________
Date ___________________
Class _____________
Lab 21: Electrolytes
Purpose
Electrolytes
Classify compounds as electrolytes by testing their conductivity in aqueous
solution.
Procedure
1. Start Virtual ChemLab and select Electrolytes from the list of assignments.
The lab will open in the Titration laboratory.
2. Click inside the Stockroom. Double-click on three reagents to move them
to the stockroom counter: NaCl, Na2CO3 (100%), and NaHCO3 (100%).
Return To Lab.
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3. For each salt, complete the following procedure: double-click the bottle
to move it to the spotlight next to the balance. Click the Beakers drawer
and place a beaker in the spotlight next to the salt bottle. Click on the
Balance area to zoom in and open the bottle by clicking on the lid
(Remove Lid). Pick up the Scoop and scoop up some salt by dragging the
scoop to the bottle and then down the face of the bottle. Pick up the
largest sample possible and place it in the beaker. Zoom Out.
Move the beaker to the stir plate. Pick up the 25 mL graduated cylinder
near the sink and hold it under the water tap until it fills. Pour the water
by dragging the cylinder to the beaker. Turn on the conductivity meter
and place the conductivity meter probe into the beaker and record the
conductivity in the Data Table. Double-click the salt bottle to place it back
on the Stockroom counter. Place the beaker in the red disposal bucket.
4. When you have completed the three reagents, return to the Stockroom.
Double-click on each bottle to return it to the shelf. Obtain three more
samples (two salts and one solution): KNO3, NH4Cl, NH3. Return to Lab.
Use the procedure from #4 for NH4Cl, and KNO3.
For the solution complete the following procedure: Place a beaker on the
spotlight left of the stir plate. Click on the Pipets drawer and double-click
a 25 mL pipet. Pick up the bottle of solution from the Stockroom shelf and
pour into the beaker until the beaker is at least one-quarter full. The
solution bottle will automatically go back to the Stockroom shelf. Click
the pipet bulb (Fill Pipet) to fill the pipet. Place the used beaker in the red
disposal bucket. Drag a new beaker to the spotlight under the pipet and
click the pipet bulb to Empty Pipet. Drag the beaker to the stir plate.
Place the conductivity meter probe into the beaker and record the
conductivity in the Data Table.
5. Return to the Stockroom. Double-click each bottle to return them to the
Stockroom shelves. Obtain two more samples: HCl and HCN. Measure
the conductivity of each solution using the procedure above, and record
the conductivity in the Table.
Mollusks, Arthropods, and Echinoderms
Electrolytes
51
4573_PH_CHEM_Lab21_pp051-052 8/11/04 12:01 PM Page 52
Name ___________________________
NaCl
Na2CO3
Date ___________________
NaHCO3
KNO3
NH4Cl
NH3
Class _____________
HCl
HCN
Electrolytes
conductivity
Analyze
1. Electrolytes are compounds that conduct electricity in aqueous solution.
Which compounds in your table are electrolytes? Which are not
electrolytes?
2. Would any of these electrolytes conduct electricity in the solid form?
Explain.
3. Are these ionic or covalent compounds? Classify each compound in the
grid as ionic or covalent. For a compound to be an electrolyte, what
must happen when it dissolves in water?
NaCl (s) S Na (aq) Cl (aq)
Na2CO3 (s) S 2Na (aq) CO32 (aq)
Write a similar balanced chemical equation for each electrolyte in the data
table.
5. After examining the chemical reactions for the electrolytes, why does
Na2CO3 have a higher conductivity than all of the other electrolytes?
52
Mollusks, Arthropods, and Echinoderms
Electrolytes
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4. When an ionic solid dissolves in water, water molecules attract the ions,
causing them to dissociate, or come apart. The resulting dissolved ions
are electrically charged particles that allow the solution to conduct
electricity. The following chemical equations represent this
phenomenon.
4573_PH_CHEM_Lab22_pp053-054 8/11/04 12:01 PM Page 53
Name ___________________________
Date ___________________
Class _____________
Lab 22: Precipitation Reactions:
Formation of Solids
Purpose
Observe, identify, and write balanced equations for precipitation reactions.
Procedure
1. Start Virtual ChemLab and select Precipitation Reactions: Formation of Solids
from the list of assignments. Lab will open in the Inorganic laboratory.
2. React each of the cations (across the top) with each of the anions (down
the left) according to the table below using the following procedures:
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Pb(NO)3 (Pb2)
Ca(NO3)2 (Ca2)
Na2CO3 (CO32)
a
f
k
Na2S (S2)
b
g
l
NaOH (OH)
c
h
m
Na2SO4 (SO42)
d
i
n
NaCl (Cl)
e
j
o
Precipitation Reactions:
Formation of Solids
AgNO3 (Ag)
a. Click in the Stockroom. Once inside the stockroom, drag a test tube
from the box and place it on the metal test tube stand. Then click on
the bottle of Ag metal ion solution on the shelf to add it to the test
tube. Click Done to send the test tube back to the lab. Return to Lab.
b. Drag the test tube containing the Ag from the blue rack to the metal
test tube stand. Click on the Divide button (the large red arrow) four
times to make four additional test tubes containing Ag. With one
test tube in the metal stand and four others in the blue rack, click on
the Na2CO3 bottle on the reagent shelf, observe what happens in the
window at the bottom left. Record your observation in the table
above. If the solution remains clear, record NR, for no reaction. Drag
this test tube to the red disposal bucket on the right.
c. Drag a second tube from the blue rack to the metal stand. Add Na2S,
record your observations and discard the tube. Continue with the
third, fourth and fifth tube, but add NaOH, Na2SO4, and NaCl
respectively. Record your observations and discard the tubes. When
you are completely finished, click on the red disposal bucket to clear
the lab.
d. Return to the stockroom and repeat steps a through c for five test
tubes of Pb2 and Ca2.
Precipitation
Mollusks, Arthropods,
Reactions: Formation
and Echinoderms
of Solids
53
4573_PH_CHEM_Lab22_pp053-054 8/11/04 12:01 PM Page 54
Name ___________________________
Date ___________________
Class _____________
Analyze
1. Translate the following word equations into balanced chemical
equations and explain how the equations represent what happens in
grid spaces a and g.
a. In grid space a, sodium carbonate reacts with silver nitrate to produce
sodium nitrate and solid silver carbonate.
b. In grid space g, sodium sulfide reacts with lead (II) nitrate to produce
sodium nitrate and solid lead (II) sulfide.
Precipitation Reactions:
Formation of Solids
2. Write a word equation to represent what happens in grid space m.
3. What happens in grid space d? What other reactions gave similar
results? Is it necessary to write an equation when no reaction occurs?
Explain.
4. Write balanced equations for all precipitation reactions you observed.
54
Mollusks, Arthropods,
Precipitation
Reactions:and
Formation
Echinoderms
of Solids
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
5. Write balanced net ionic equations for all precipitation reactions you
observed.
4573_PH_CHEM_Lab23_pp055-058 8/11/04 12:01 PM Page 55
Name ___________________________
Date ___________________
Class _____________
Lab 23: Identification of
Cations in Solution
Purpose
Identify the ions in an unknown solution through the application of
chemical tests.
Background
The process of determining the composition of a sample of matter by
conducting a chemical test is called qualitative analysis. Solutions of
unknown ions can be subjected to chemical tests and the results can be
compared to the results given by known ions. By conducting the
appropriate tests and applying logic, the identities of the ions present in
an unknown solution can be determined.
In this experiment, you will observe several types of chemical reactions
commonly used as tests in qualitative analysis. These reactions include the
color of a flame as the chemical is placed in the flame and the formation of
a precipitate (solid).
Procedure
2. Enter the stockroom by clicking inside the Stockroom window. Once
inside the stockroom, drag a test tube from the box and place it on the
metal test tube stand. You can then click on a bottle of metal ion solution
on the shelf to add it to the test tube. When you have added one metal
ion, click Done to send the test tube back to the lab. Repeat this process
with a new metal ion. Continue doing this until you have sent one test
tube for each of the following metal ions to the lab: Na, K, and a
Na/K mixture. Fill one test tube with just water by clicking on the
bottle of distilled water. Now click on the Return to Lab arrow.
Identification of
Cations in Solution
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
1. Start Virtual ChemLab and select Identification of Cations in Solution from
the list of assignments. The lab will open in the Inorganic laboratory.
3. When you return to the lab you should note that you have four test tubes.
Just above the periodic table there is a handle. Click on the handle to pull
down the TV monitor. With the monitor down you can drag your cursor
over each test tube to identify what metal ion the test tube contains, and
you will see a picture of what it looks like in the lower left corner.
Part 1, Flame Tests
1. You will use two of the buttons across the bottom, Flame and Flame w/
Cobalt (blue glass held in front of the flame.) A test tube must be moved
from the blue test tube rack to the metal test tube stand in order to
perform the flame test. You can drag a test tube from the blue rack to the
metal test tube stand to switch places with a test tube in the metal test
tube stand.
Mollusks,
Identification
Arthropods,
of Cations
and Echinoderms
in Solution
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Name ___________________________
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2. Flame test sodium ion only. Flame w/ Cobalt test sodium ion only. Record
your observations.
3. Flame test potassium ion only. Flame w/ Cobalt test potassium ion only.
Record your observations.
4. Flame and Flame w/ Cobalt test a mixture of sodium and potassium.
Record your observations.
6. Return to the Stockroom. On the right end of the supply shelf is a button
labeled Unknowns. Click on the Unknowns label to create a test tube with
an unknown. Now click on Na and K. On the left side make the
minimum 0 and maximum 2. Click the Save button. An unknown
test tube titled Practice will show in the blue rack. Drag the practice
unknown test tube from the blue rack to place it in the metal stand and
click Done to send it to the lab. Return to Lab.
7. Flame test the Practice Unknown and determine if it contains sodium or
potassium or both or neither. Click on the Lab Book. On the left page,
click the Report button, Submit, then OK. If the ion button is green, you
correctly determined whether the ion was present or not. If the ion
button is red you did not make the correct analysis. Click the red
disposal bucket to clear the lab. If you want to repeat with a new
practice unknown, return to the stockroom and retrieve it from the blue
rack. When you are confident that you can make a correct determination
with sodium and potassium, proceed to Part 2.
Part 2, Insoluble Chlorides
1. Return to the Stockroom. In a new test tube, place three ions: Ag, Hg22,
and Pb2. (There is Hg2 and Hg22 on the shelf. Make sure you obtain
Hg22.) Return to Lab. As you proceed with the chemical analysis watch
the TV screen to see the chemistry involved in the chemical reactions.
56
Mollusks, Arthropods,
Identification
of Cationsand
in Solution
Echinoderms
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Identification of
Cations in Solution
5. Flame test a blank (distilled water) with and without cobalt glass to get a
feel for what it looks like with no chemicals other than water. Record
your observations.
4573_PH_CHEM_Lab23_pp055-058 8/11/04 12:01 PM Page 57
Name ___________________________
Date ___________________
Class _____________
2. Move the test tube to the metal stand. Click the reagent bottle NaCl to
add chloride to the test tube. What observations can you make?
Click the Centrifuge button. What observations can you make?
Each of the three ions form insoluble precipitates (solids) with chloride.
If the solution turns cloudy white it indicates that at least one of the
three ions is present. Now, we must determine which one.
3. Turn the heat on with the Heat button. Observe the TV screen. What
happened? If you cannot tell, turn the heat on and off while observing
the TV screen.
With the heat turned on, click Decant. Drag your cursor over the new test
tube in the rack. What appears on the TV screen? What appears in the
picture window?
This is the test for Pb2. If heated, it is soluble. When cooled it becomes
insoluble.
Addition of ammonia produces a diammine silver complex ion which is
soluble. The mercury produces a black solid. This is the test for mercury.
Identification of
Cations in Solution
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4. Turn off the Heat. Click the NH3 bottle on the reagent shelf. What do you
observe?
5. Centrifuge and then Decant to pour the silver ion into another test tube.
Move the tube with the black mercury solid to the red disposal bucket.
Move the tube containing silver back to the metal stand. Click the pH 4
reagent bottle. What do you observe?
The silver ion is soluble as the diammine silver complex ion in pH 10
and is insoluble as AgCl in pH 4. You can click alternately on each of the
pH bottles to confirm this test for silver ion.
6. Return to the Stockroom and create an unknown with Ag, Hg22, and
Pb2. Use minimum 0 and maximum 3. Return to the lab and
complete the analysis. Report your results in the Lab Book and check to
determine if you can correctly identify these three ions. When you are
confident that you can correctly identify Ag, Hg22, and Pb2 proceed
to Part 3.
Identification of Cations in Solution
57
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Name ___________________________
Date ___________________
Class _____________
Part 3, Selected Transition Metal Ions
1. Return to the Stockroom. In a new test tube, place three ions: Co2, Cr3,
and Cu2. Return to Lab. As you proceed with the chemical analysis watch
the TV screen to see the chemistry involved in the chemical reactions.
2. Move the test tube to the metal stand. Click the NaOH bottle on the
reagent shelf. What observations can you make?
3. Click Centrifuge and Decant. What observations can you make as you
drag your cursor over each test tube?
This is the test for chromium. If the new test tube in the blue rack is
green when decanted then chromium is present. You can confirm it by
placing the clear green test tube in the metal stand and clicking pH 10
and then adding HNO3. What observations can you make?
5. Centrifuge and Decant. Add HNO3 to the tube in the metal stand
containing the precipitate. What observations can you make?
This is the confirmatory test for cobalt ion (Co2).
6. Place the test tube from the blue rack which is the decant from step # 5
in the metal stand. Add HNO3. What observations can you make?
This is the confirmatory test for copper.
7. Return to the Stockroom and create an unknown with Co2, Cr3, and
Cu2. Use minimum 0 and maximum 3. Return to the lab and
complete the analysis. Report your results in the Lab Book and check to
determine if you can correctly identify these three ions.
58
Identification of Cations in Solution
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Identification of
Cations in Solution
4. With the test tube containing the precipitate in the metal stand, add
NH3. What observations can you make?
4573_PH_CHEM_Lab24_pp059
8/11/04
12:00 PM
Page 59
Name ___________________________
Date ___________________
Class _____________
Lab 24: Qualitative Analysis
Purpose
Develop a systematic panel of chemical tests to identify an unknown
solution of eight metal cations.
Background
In the Identification of Cations in Solution experiment, you learned how to
identify eight metal cations in three groups. In this experiment you will
complete a qualitative analysis scheme using the information learned in the
previous experiment with an unknown solution containing one to eight of
the ions.
Procedure
1. Start Virtual ChemLab and select Qualitative Analysis from the list of
assignments. The lab will open in the Inorganic laboratory.
3. Move the test tube to the metal stand and click the Divide button three
times. Move the three new test tubes to the right end of the blue rack.
These three tubes are duplicates of your unknown. If you make a
mistake and need to begin again, you can use one of these. Before you
use the last one make additional duplicates.
4. From your experience in the previous lab, you know how to analyze the
three different groups: flame tests, insoluble chlorides, and selected
transition metals. Now that all three groups are combined you will still
analyze the unknown as three separate groups. First, flame test for Na
and/or K. Remember, neither may be present and one of the other six
ions will have a unique flame test that you have not seen before. Second,
test for the insoluble chlorides. If you obtain a precipitate when adding
NaCl then Centrifuge and Decant. The decant will contain the third
group. Third, complete the analysis on the transition metals.
5. Report your results in the Lab Book and check to see if you correctly
identified the presence or absence of each of the eight cations.
Qualitative
Analysis
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2. Click to enter the Stockroom. Create an unknown with Na, K,
Ag, Hg22, Pb2, Co2, Cr3, and Cu2. Set minimum 0 and
maximum 8. This means that you could have only water or any
number of the ions up to all eight. Click Save. Move the Practice
Unknown to the metal stand and Return to Lab.
Mollusks, Arthropods,
Qualitative
and Echinoderms
Analysis
59
4573_PH_CHEM_Lab25_pp060-062 8/11/04 12:00 PM Page 60
Name ___________________________
Date ___________________
Class _____________
Lab 25: Study of Acid-Base Titrations
Study of Acid-Base
Titrations
Purpose
Observe the changes that occur during the titration of a strong acid and
strong base.
Background
Titrations provide a method of quantitatively measuring the concentration
of an unknown solution. In an acid-base titration, this is done by delivering
a titrant of known concentration to an analyte of known volume. (The
concentration of an unknown titrant can also be determined by titration
with an analyte of known concentration and volume.) Titration curves
(graphs of volume vs. pH) have characteristic shapes. By comparison, the
graph can be used to determine the strength or weakness of an acid or
base. The equivalence point of the titration, or the point where the analyte
has been completely consumed by the titrant, is identified by the point
where the pH changes rapidly over a small volume of titrant delivery.
There is a steep incline or decline at this point of the titration curve. In this
assignment, you will observe this titration curve by titrating the strong acid
HCl with the strong base NaOH.
Procedure
1. Start Virtual ChemLab and select Study of Acid-Base Titrations from the list
of assignments. The lab will open in the Titration laboratory.
3. The buret will be filled with NaOH. The horizontal position of the orange
handle is off for the stopcock. Click the Save button in the Buret Zoom View
window. Open the stopcock by pulling down on the orange handle. The
vertical position delivers solution the fastest with three intermediate rates
in between. Turn the stopcock to one of the fastest positions. Observe the
titration curve. When the volume reaches 35 mL, double-click the
stopcock to stop the titration. Click Stop in the Buret Zoom View. A blue
data link will be created in the lab book, click on it to view the data.
Analyze
1. The beaker contains 0.3000 M HCl and the buret contains 0.3000 M
NaOH. Write a complete balanced equation for the neutralization
reaction between HCl and NaOH.
The following questions can be answered by examining the Plot and
Data Viewer windows.
60
Mollusks,
Study
of Acid-Base
Arthropods,
Titrations
and Echinoderms
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2. Click the Lab Book to open it; if other students have left data links
highlight and delete them.
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Name ___________________________
Date ___________________
Class _____________
2. What were the pH and color of the solution at the beginning of the
titration?
Study of Acid-Base
Titrations
3. What were the pH and color of the solution at the end of the titration?
4. Examine the graph of the pH vs volume. Sketch the shape of the titration
graph of pH vs volume (blue line).
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5. What happens to the pH around 25 mL?
6. What caused the change observed in Question 4?
Mollusks, Arthropods,
Study of Acid-Base
and Echinoderms
Titrations
61
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Name ___________________________
Date ___________________
Class _____________
Study of Acid-Base
Titrations
7. Examine the graph of the conductivity vs volume. Sketch the shape of
the titration graph of conductivity vs volume (red line).
8. What happens to the conductivity during the titration?
9. What caused the change observed in Question 8?
Complete a similar laboratory activity except using a polyprotic acid.
Click in the Stockroom. Click on the clipboard and select Polyprotic Acid
Strong Base.
1. What observations can you make about the graph of a titration with a
polyprotic acid?
62
Study of Acid-Base Titrations
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Further Investigation
4573_PH_CHEM_Lab26_pp063-065
8/11/04
11:59 AM
Page 63
Name ___________________________
Date ___________________
Class _____________
Lab 26: Acid-Base Titrations
Purpose
Standardize a NaOH solution and measure the molarity of an unknown
acetic acid solution by titration with standardized NaOH.
Background
Acid-Base Titrations
Titrations provide a method of quantitatively measuring the concentration
of an unknown solution. In an acid-base titration, this is done by delivering
a titrant of known concentration to an analyte of known volume. (The
concentration of an unknown titrant can also be determined by titration
with an analyte of known concentration and volume.) Titration curves
(graphs of volume vs. pH) have characteristic shapes. By comparison, the
graph can be used to determine the strength or weakness of an acid or
base. The equivalence point of the titration, or where the analyte has been
completely consumed by the titrant, is identified as the point where the pH
changes rapidly over a small volume of titrant delivery. There is a steep
incline or decline at this point of the titration curve. In this assignment, you
will determine the molarity of an unknown solution of NaOH by using a
primary standard, potassium hydrogen phthalate (KHP). You will then use
a standardized solution of NaOH to determine the molarity of an unknown
solution of acetic acid.
Procedure
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Part 1
1. Start Virtual ChemLab and select Acid-Base Titrations from the list of
assignments. The lab will open in the Titrations laboratory.
2. Click the Lab Book to open it. Click the Buret Zoom View window to bring
it to the front. Click the Beakers drawer and place a beaker in the
spotlight next to the balance. Click on the Balance area to zoom in, open
the bottle of KHP by clicking on the lid (Remove Lid). Drag the beaker to
the balance to place it on the balance pan; tare the balance. Pick up the
Scoop and scoop out some KHP; as you drag your cursor and the scoop
down the face of the bottle it picks up more. Select the largest sample
possible and drag the scoop to the beaker until it snaps in place which
will place the KHP in the beaker (about 1 g). Unload the full scoop twice
into the beaker so you have around 2.0 g and record the mass of the
sample in the Data Table. Place the beaker in the spotlight outside the
balance and Zoom Out.
3. Drag the beaker to the sink and hold it under the tap to add a small
amount of water. Place it on the stir plate and add the calibrated pH
meter probe to the beaker. Add Phenolphthalein for the indicator.
Mollusks, Arthropods,
Acid-Base
and Echinoderms
Titrations
63
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Page 64
Name ___________________________
Date ___________________
Class _____________
4. The buret will be filled with NaOH. Click the Save button in the Buret
Zoom View window so the titration data be saved. The horizontal
position of the orange handle is off for the stopcock. Open the stopcock
by pulling down on the orange handle. The vertical position delivers
solution the fastest with three intermediate rates in between. Turn the
stopcock to one of the fastest positions. Observe the titration curve.
When the blue line begins to turn up, double-click the stopcock to turn it
off. Move the stopcock down one position to add volume drop by drop.
Acid-Base Titrations
There are two methods for determining the volume at the equivalence
point: (1) Stop the titration when a color change occurs. Click the Stop
button in the Buret Zoom View. A blue data link will appear in the lab
book. Click the blue data link to open the Data View window. Scroll
down to the last data entry and record the volume at the equivalence
point in Data Table 1; OR (2) Add drops slowly through the equivalence
point until the pH reaches approximately 12. Click the Stop button in the
Buret Zoom View. A blue data link will appear in the lab book. Click the
blue data link to open the Data View window. Click Select All button to
copy and paste the data to a spreadsheet. Plot the first derivative of pH
vs. volume. The peak will indicate the volume of the equivalence point
since this is where the pH is changing the most as volume changes.
Repeat at least two additional times, and record your data in the table.
The molecular weight of KHP is 204.22 g/mol.
mass KHP (g)
volume NaOH (mL)
molarity NaOH (mol/L)
1
2
Analyze
1. Write a balanced chemical equation for the reaction of KHP and NaOH.
2. What is the average molarity of the unknown NaOH for your closest
three titrations?
64
Mollusks, Arthropods,
Acid-Base
Titrations and Echinoderms
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Trial
4573_PH_CHEM_Lab26_pp063-065
8/11/04
11:59 AM
Page 65
Name ___________________________
Date ___________________
Class _____________
Part 2
1. Click in the Stockroom. Click on the clipboard and select Weak Acid Strong
Base Unknown. The base is 0.3060 M NaOH and the buret has been filled
with it. The weak acid is an unknown concentration of acetic acid. 25 mL
of acetic acid has been added to the beaker. The indicator is
phenolphthalein and has already been added. The pH meter has been
turned on and calibrated.
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Acid-Base Titrations
2. Open your lab book and click the Save button on the Buret Zoom View
window before starting the titration. Begin the titration by opening the
stopcock on the buret. Observe what happens to the pH as the titration
proceeds. As the titration nears the end point, decrease the rate of
delivery to the slowest rate. Immediately after the color of the indicator
changes, stop the titration and read the amount of titrant that has been
delivered from the buret by clicking Stop in the Buret Zoom View
window. Open the blue data link in the lab book and determine the
volume at the equivalence point using one of the methods described in
Part 1. Record the volume in the table.
3. Move the used beaker to the disposal bucket and repeat the experiment
at least two more times. Fill the buret with NaOH. Place a beaker in the
spotlight left of the stir plate and fill the beaker half full with acetic acid
(HAc). Open the Pipets drawer and double-click on a 25 mL pipet. Click
the pipet bulb (Fill Pipet) to fill the pipet. Move the beaker to the
spotlight right of the stir plate and drag a new beaker to the spotlight
under the pipet and click the pipet bulb to Empty Pipet. Drag the beaker
to the stir plate. Place the pH meter probe in the beaker and add
phenolphthalein indicator. Make certain the lab book is open and click
Save in the Buret Zoom View.
Trial
volume NaOH
(mL)
molarity NaOH
(mol/L)
volume HAc
(mL)
molarity HAc
(mol/L)
1
2
Analyze
1. Write a balanced equation for the reaction between HAc and NaOH.
2. What is the average molarity of the unknown acetic acid solution?
Mollusks, Arthropods,
Acid-Base
and Echinoderms
Titrations
65
4573_PH_CHEM_Lab27_pp066-067 8/11/04 12:24 PM Page 66
Name ___________________________
Date ___________________
Class _____________
Lab 27: Ionization Constants of
Weak Acids
Purpose
Measure ionization constants of weak acids such as bromocresol green (BCG).
Procedure
1. Start Virtual ChemLab and select Ionization Constants of Weak Acids from
the list of assignments. The lab will open in the Titration laboratory.
2. Using the bottle of 0.1104 M NaOH, fill the buret. The bottle will snap
into position to pour and remain until buret is full. Click the buret to
open the buret window.
3. Click the Beakers drawer and place a beaker in the spotlight to the left of
the stir plate. Fill the beaker half full with 0.1031 M HAc. Open the Pipets
drawer and double-click on a 10 mL pipet. Click the pipet bulb (Fill
Pipet) to fill. Move the beaker to the spotlight to the right of the stir plate
and place a new beaker under the pipet and click the pipet bulb to
Empty Pipet. Move the beaker with 10 mL HAc and place it on the stir
plate. Click the Stir Plate Switch to turn it on. Place the calibrated pH
meter probe in the beaker. Add Bromocresol Green to the beaker (doubleclick on the bottle labeled Bro G).
5. The horizontal position of the orange handle is off for the stopcock.
Open the stopcock by pulling down on the orange handle. The vertical
position delivers solution the fastest with three intermediate rates in
between off. Turn the stopcock two stops down from the off position.
When there is a color change, double-click the stopcock to turn it off. If it
is necessary to repeat the experiment, do not forget to refill the buret
with NaOH and place the pH meter in the beaker on the stir plate.
6. What are the color and pH of the solution?
Continue to add NaOH as before. What is the final color of the solution?
66
Mollusks, Arthropods,
Ionization
Constants ofand
Weak
Echinoderms
Acids
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Ionization Constants of
Weak Acids
4. What are the color and pH of the solution?
4573_PH_CHEM_Lab27_pp066-067 8/11/04 12:24 PM Page 67
Name ___________________________
Date ___________________
Class _____________
Analyze
1. An acid-base indicator is usually a weak acid with a characteristic color.
Because bromocresol green is an acid, it is convenient to represent its
complex formula as HBCG. HBCG ionizes in water according to the
following equation:
HBCG H2O S BCG H3O
(yellow)
(blue)
The Ka (the equilibrium constant for the acid) expression is
Ka 3BCG4 3H3O 4
3HBCG4
When [BCG] [HBCG], then Ka [H3O]. From the pH of the
solution the [H3O] and Ka can be determined.
2. What color is an equal mixture of HBCG and BCG? What is the pH at
the first appearance of this color?
3. What is the Ka for bromocresol green?
Design and carry out an experiment to measure the Ka of bromocresol
purple and methyl orange.
Ionization Constants of
Weak Acids
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You’re the Chemist
Mollusks,
Ionization
Arthropods,
Constants
andofEchinoderms
Weak Acids
67
4573_PH_CHEM_Lab28_pp068-069 8/11/04 12:23 PM Page 68
Name ___________________________
Date ___________________
Class _____________
Lab 28: Analysis of Baking Soda
Purpose
Determine the mass of sodium hydrogen carbonate in a sample of baking
soda using stoichiometry.
Procedure
1. Start Virtual ChemLab and select Analysis of Baking Soda from the list of
assignments. The lab will open in the Titration laboratory.
Analysis of Baking Soda
There are two methods for determining the volume at the equivalence
point: (1) Stop the titration when a color change occurs. Click the Stop
button in the Buret Zoom View. A blue data link will appear in the lab
book. Click the blue data link to open the Data View window. Scroll
down to the last data entry and record the volume at the equivalence
point in Data Table 1; OR (2) Add drops slowly through the equivalence
point until the pH reaches approximately 2. Click the Stop button in the
Buret Zoom View. A blue data link will appear in the lab book. Click the
blue data link to open the Data View window. Click Select All button to
copy and paste the data to a spreadsheet. Plot the first derivative of pH
vs. volume. The peak will indicate the volume of the equivalence point
since this is where the pH is changing the most as volume changes.
mass unknown sample (g)
68
volume HCl (mL)
Mollusks,ofArthropods,
Analysis
Baking Soda
and Echinoderms
molarity HCl (mol/L)
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2. The beaker has 1.5000 g of the impure solid NaHCO3 and is filled with
water to make a volume of 25.00 mL. The indicator methyl orange is in
the beaker. The calibrated pH meter is in the beaker, the graph window
is open. Click on the Lab Book to open it and delete any previous data
saved by another students. Click on the Buret Zoom View window and
the pH meter window to bring them to the front. Click the Save button
on the graph window before starting the titration. Begin the titration by
opening the stopcock on the buret. Observe what happens to the pH as
the titration proceeds. It is important that the volume increments and
pH measurements near the equivalence point are small enough so the
equivalence point can be determined as closely as possible. When the
graph starts to curve downward decrease the rate of delivery to the
slowest rate. Immediately after the color of the indicator changes, stop
the titration by double-clicking the stopcock. Click the Stop button in the
Buret Zoom View window. Click the blue data link in the lab book.
Scroll down the Data Viewer window to the last volume entry in the left
column and record the volume in the Table.
4573_PH_CHEM_Lab28_pp068-069 8/11/04 12:23 PM Page 69
Name ___________________________
Date ___________________
Class _____________
Analyze
1. Write a balanced chemical equation for the reaction between NaHCO3
and HCl.
2. Calculate the moles of HCl by multiplying the volume of HCl in liters
and the molarity of HCl in mol/L. (Keep four significant digits in all of
the calculations.)
3. The moles of HCl can be converted to moles of NaHCO3 using the
coefficients from the balanced equation. What is the mole to mole ratio of
HCl to NaHCO3? How many moles of NaHCO3 are present in the sample?
4. Calculate the grams of NaHCO3 by multiplying the moles of NaHCO3
by the molecular weight of NaHCO3 (84 g/mol).
Mollusks, Arthropods,
Analysis
and
ofEchinoderms
Baking Soda
69
Analysis of Baking Soda
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5. The percent NaHCO3 present in the sample can be calculated by
dividing the mass of NaHCO3 from Question 4 by the mass of the
sample from the Table and multiplying by 100. What is the percent
NaHCO3?
4573_PH_CHEM_Lab29_pp070-071 8/11/04 12:23 PM Page 70
Name ___________________________
Date ___________________
Class _____________
Molecular Weight
Determination by AcidBase Titration
Lab 29: Molecular Weight Determination
by Acid-Base Titration
Purpose
Determine the molecular weight of a solid acid by titration methods.
Background
Titrations provide a method of measuring the concentration of an
unknown solution. In an acid-base titration, a titrant of known
concentration is added to an analyte of known volume. (The concentration
of an unknown titrant can also be determined by titration with an analyte
of known concentration and volume.) Titration curves (graphs of volume
vs. pH) have characteristic shapes. The graph can be used to determine the
strength or weakness of an acid or base. The equivalence point of the
titration, where the analyte has been completely consumed by the titrant, is
identified as the point where the pH changes rapidly over a small volume
of titrant delivery. There is a steep incline or decline in the titration curve at
this point of the titration curve. In this assignment, you will determine the
molecular weight of an unknown acid powder by weighing the solid to
determine the mass and titrating to determine the moles of acid.
Procedure
2. Click the Lab Book to open it. Click the Buret Zoom View window to bring
it to the front. Click the Beakers drawer and move a beaker to the
spotlight next to the balance. Click on the Balance area to zoom in, open
the bottle by clicking on the lid (Remove Lid). Drag the beaker to the
balance to place it on the balance pan; Tare the balance. Pick up the Scoop
and scoop out some sample; as you drag your cursor and the scoop
down the face of the bottle it picks up more. Select the largest sample
possible and drag the scoop to the beaker until it snaps in place which
will place the sample in the beaker (about 1 g). Record the mass of the
sample in the Table. Place the beaker in the spotlight outside the balance
and Zoom Out.
3. Drag the beaker to the sink and hold it under the tap to add a small
amount of water. Place it on the stir plate and add the calibrated pH
meter probe to the beaker. Add Phenolphthalein for the indicator.
4. The buret will be filled with NaOH. The horizontal position of the
orange handle is off for the stopcock. Click the Save button in the Buret
Zoom View window. Open the stopcock by pulling down on the orange
handle. The vertical position delivers solution the fastest with three
intermediate rates in between. Turn the stopcock to one of the fastest
70
Mollusks, Arthropods,
Molecular
Weight Determination
and Echinoderms
by Acid-Base Titration
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
1. Start Virtual ChemLab and select Molecular Weight Determination by AcidBase Titration from the list of assignments. The lab will open in the
Titration laboratory.
4573_PH_CHEM_Lab29_pp070-071 8/11/04 12:23 PM Page 71
Name ___________________________
Date ___________________
Class _____________
Molecular Weight
Determination by AcidBase Titration
positions. Observe the titration curve. When the blue line begins to turn
up, double-click the stopcock to turn it off. Move the stopcock down one
position to add solution drop by drop.
There are two methods for determining the volume at the equivalence
point: (1) Stop the titration when a color change occurs. Click the Stop
button in the Buret Zoom View. A blue data link will appear in the lab
book. Click the blue data link to open the Data View window. Scroll
down to the last data entry and record the volume at the equivalence
point in Data Table 1. OR (2) Add drops slowly through the equivalence
point until the pH reaches approximately 12. Click the Stop button in the
Buret Zoom View. A blue data link will appear in the lab book. Click the
blue data link to open the Data View window. Click Select All button to
copy and paste the data to a spreadsheet. Plot the first derivative of pH
vs volume. The peak will indicate the volume of the equivalence point
since this is where the pH is changing the most as volume changes.
Repeat at least two additional times, and record your data in the table.
Do not forget to refill the buret with NaOH and place the pH meter in
the beaker and add indicator each time.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
The concentration of the NaOH is 0.1961 M. The moles of acid are
calculated by multiplying the volume of the NaOH (in L) by the
molarity of the NaOH. Dividing the mass of the acid sample by the
moles will provide the molecular weight in g/mol.
Trial
mass of acid sample
volume NaOH
(mL)
molarity NaOH
(mol/L)
(g/mol)
molecular weight
1
2
3
5. What is the average molecular weight of your three closest answers?
6. Calculate your percent error by the following formula using only the
values used in the average if you complete more than three trials:
% Error highest answer lowest answer
100
average
Molecular Weight
Mollusks,
Determination
Arthropods,
by Acid-Base
and Echinoderms
Titration
71
4573_PH_CHEM_Lab30_pp072-074 8/11/04 12:22 PM Page 72
Name ___________________________
Date ___________________
Class _____________
Lab 30: Redox Titrations: Determination
of Iron
Purpose
Determine the percent composition of iron in a sample using an oxidationreduction titration with potassium permanganate.
Redox Titrations:
Determination of Iron
Background
Titrations provide a method of quantitatively measuring the concentration
of an unknown solution. In an acid-base titration, this is done by delivering
a titrant of known concentration to an analyte of known volume. (The
concentration of an unknown titrant can also be determined by titration
with an analyte of known concentration and volume.) Reduction-oxidation
(redox) titrations can also be used to measure concentrations. In redox
titrations, voltages of the mixture of an oxidant and reductant can also be
measured as the titration proceeds. All titration curves have characteristic
shapes. The equivalence point of the titration, or the point where the
analyte has been completely consumed by the titrant, is identified by the
point where the voltage changes rapidly over a small volume of titrant
delivered. There is a steep incline or decline at this point of the titration
curve. In this assignment, you will observe this titration curve by titrating
KMnO4 with FeCl2.
Procedure
2. Record the FeCl2 Unknown # in the Data Table. Click the Lab Book to
open it. Click the Buret Zoom View window to bring it to the front. Click
the Beakers drawer and place a beaker in the spotlight next to the
balance. Move the FeCl2 bottle to the spotlight next to the balance. Click
on the Balance area to zoom in and open the bottle of FeCl2 by clicking
on the lid (Remove Lid). Drag the beaker to the balance to place it on the
balance pan. Tare the balance. Pick up the Scoop and scoop up some
sample by dragging the scoop to the bottle and then down the face of
the bottle. Pick up the largest sample possible and place it in the beaker
(about 1 g). Continue dragging the scoop to the beaker until it snaps in
place which will place the sample in the beaker. Unload the full scoop
twice into the beaker so you have around 2.0 g and record the mass of
the sample in the Table. Place the beaker in the spotlight outside the
balance and Zoom Out.
3. Place the beaker on the stir plate. Drag the 50 mL graduated cylinder
under the tap in the sink and fill it with distilled water. Pour the water
into the beaker on the stir plate. Place the electrode in the beaker and turn
on the volt meter.
72
Mollusks,
Redox
Titrations:
Arthropods,
Determination
and Echinoderms
of Iron
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
1. Start Virtual ChemLab and select Redox Titrations: Determination of Iron
from the list of assignments. The lab will open in the Titrations
laboratory.
4573_PH_CHEM_Lab30_pp072-074 8/11/04 12:22 PM Page 73
Name ___________________________
Date ___________________
Class _____________
4. The buret will be filled with KMnO4. The horizontal position of the
orange handle is off for the stopcock. Click Save on the Buret window to
save the data to the lab book. Open the stopcock by pulling down on the
orange handle. The vertical position delivers volume the fastest with
three intermediate rates in between. Turn the stopcock to one of the
fastest positions. Observe the titration curve. When the blue line begins
to turn up, double-click the stopcock to turn it off. Move the stopcock
down one position to add volume drop by drop.
Redox Titrations:
Determination of Iron
There are two methods for determining the volume at the equivalence
point: (1) Stop the titration when a color change occurs. Click the Stop
button in the Buret Zoom View. A blue data link will appear in the lab
book. Click the blue data link to open the Data View window. Scroll
down to the last data entry and record the volume at the equivalence
point in the Data Table; OR (2) Add drops slowly through the
equivalence point until the voltage reaches approximately 1.50 V. Click
the Stop button in the Buret Zoom View. A blue data link will appear in
the lab book. Click the blue data link to open the Data View window.
Click the Select All button to copy and paste the data to a spreadsheet.
Plot the first derivative of voltage vs. volume. The peak will indicate the
volume of the equivalence point since it is where the voltage is changing
the most as volume changes.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
5. Sketch the graph of the titration below. Label the axes.
The reduction potential of Fe2 is 0.732 volts. The reduction potential of
MnO4 in acidic solution is 1.507 volts. If you titrate FeCl2 into KMnO4,
what happens to the voltage of the solution as the titration starts and
proceeds to the end?
Mollusks,
Redox Titrations:
Arthropods,
Determination
and Echinoderms
of Iron
73
4573_PH_CHEM_Lab30_pp072-074 8/11/04 12:22 PM Page 74
Name ___________________________
Date ___________________
Class _____________
Repeat the titration at least two additional times recording data in the
Table. Do not forget to refill the buret with KMnO4, place the voltage
meter in the beaker and add water each time.
The molecular weight of FeCl2 is 151.91 g/mol.
Unknown # _____
Trial
mass FeCl2 (g)
volume KMnO4 (mL)
molarity KMnO4 (mol/L)
1
2
Redox Titrations:
Determination of Iron
3
Analyze
1. Write a balanced net ionic equation for the reaction in acidic solution of
FeCl2 and KMnO4 (Fe2 becomes Fe3 and MnO4 becomes Mn2).
2. The moles of MnO4 can be determined by multiplying the volume of
MnO4 required to reach the endpoint multiplied by the molarity of the
MnO4. What are the moles of MnO4?
4. The mass of FeCl2 in the sample can be calculated by multiplying the
moles of FeCl2 by the molecular weight of FeCl2. What is the mass of
FeCl2 in the sample?
5. The percent iron in the unknown sample can be determined by dividing
the mass of FeCl2 in the sample by the total mass of the unknown
sample. What is the percent iron in your unknown sample?
6. What is the average percent iron in the unknown sample using your best
three answers?
74
Redox Titrations: Determination of Iron
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
3. The moles of FeCl2 can be calculated by using the mole ratio from the
balanced equation. What are the moles of FeCl2?