Download 1. How many moles are 1.20 x 10 25 atoms of

The Mole (Pre-AP)
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What is a Mole?
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Define what a mole measures
Memorize Avogadro’s number – 6.022x1023
Identify the representative particle of a
chemical as a molecule, formula unit, atom or
ion
 Differentiate these molar values: A mole is 6.02
x 1023 particles A mole’s mass equals its
formula mass. The volume of a mole of gas is
22.4L
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Mole Conversions
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Determine the molar mass of an element,
compound or molecule.
Convert between moles and number of
particles.
Convert between moles and mass.
Convert between mass and number of particles.
Apply the rules of sig figs when solving for
your answers.
Convert between moles and liters for gases.
Convert between moles, mass, particles and
liters at all levels of difficulty.
Short informational
video about the
mole
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Empirical and Molecular
Formulas
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Differentiate between empirical and
molecular formulas.
Determine percent composition of
each element in a compound.
Determine molecular formula given
empirical and MW.
Determine empirical formula given
percent composition.
Determine empirical formula from
combustion analysis.
Calculating Empirical Formula
Determining E.F.
From Percent Composition
using Combustion
Analysis
Warm-ups
Wed, Jan. 4
Thurs, Jan 5
Fri, Jan. 6
Mon, Jan. 9
Tues, Jan. 10
Wed, Jan. 11
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Practice Problems
Solving Problems with Avagadro’s Number
#1. How many moles are 1.20 x 1025 atoms of phosphorous?
#2. How many atoms are in 0.750 mol of Zn?
#3. How many molecules are in 0.400 mol N2O5?
#4. How many moles are contained in 1.20 x 1024 molecules CO2?
#5. How many ammonium ions (NH4+) are in 0.036 mol ammonium phosphate?
#6. How many total carbon atoms are in a mixture of 3.00 mol acetylene (C2H2) and 0.700 mol carbon monoxide?
Determining Molar Mass
(A) CH3
(F) PbCH2COOH
(B) C2H6
(G) Al2O3
(C) C2H5OH
(H) Na2S
(D) CuCO3
(I) CaCO3
(E) H2SO4
(J) NaHCO3
Mole-Mass and Mole-Volume Relationships
#7. What is the molar mass of CH3OH?
#8. What are the grams of magnesium phosphate?
#9. What is the molar mass of ammonium sulfate?
Mole – Mass Conversions
1 mol = molar mass
#10. Find the mass in grams of 3.32 mol of K.
#11. Find the mass in grams of 15.0 mol of sulfuric acid.
#12. Find the number of moles in 187 g of aluminum.
#13. Find the number of moles in 11.0 g of methane (CH4).
Multi-Step Mole Problems:
#14. Calculate the number of molecules present in 4.29 g of nitrogen dioxide.
#15. Calculate the number of moles of sulfur atoms present in 2.01g of sodium sulfide.
#16. Calculate the mass in grams of 2.49 x 1020 carbon dioxide molecules.
#17. Calculate the grams of carbon in 12.2 mol of sucrose, C12H22O11.
Molar Volume of a Gas
1 mol of any gas at STP = 22.4 L (Used for gases only!)
#18. What is the volume (liters) at STP of 0.960 mol of methane, CH4?
0.960 mol = ? L
#19. At STP, how many moles are in 0.542 mL of neon gas?
Gas Density
#20. The density of nitrogen gas at STP is 1.25 g/L. Find the mass of nitrogen gas.
#21. Calculate the density of sulfur dioxide (SO2) gas at STP.
Percent Composition
#22. Find the % composition for a compound that is formed from 222.6 g of Na and 77.4 g O.
#23. What is the percent composition of calcium acetate (Ca(C2H3O2)2)?
Bubble Gum - % Composition of Sugar:
Mass before chewing: ______
Mass after chewing:_______
% sugar in bubble gum: _____
Calculating Empirical Formulas
#24. A compound is 79.8% C and 20.2% H. Find its empirical formula.
#25. An oxide of aluminum is formed by the complete reaction of 4.151g of aluminum with 3.692 g of oxygen.
Calculate the empirical formula for this compound.
Calculating Molecular Formulas
#26. A white powder is analyzed and found to have the empirical formula P2O5. The compound has a molar mass
of 283.9 g. What is the compound’s molecular formula?
#27. A compound used as an additive for gasoline to help prevent engine knock shows the following percentage
composition:
71.65% Cl
24.27% C
4.07% H
The molar mass is known to be 98.96 g. Determine the empirical formula and the molecular formula for this
compound.
Combustion Analysis
#28. Complete combustion (reaction with O2) of a sample of propane gas (contains only C and H) produced 2.641
g of CO2 and 1.442 g of water as the only products. Find the empirical formula for propane.
#29. Suppose you isolate an acid from clover leaves and know that it contains only the elements C, H, and O.
Heating 0.513g of the acid in oxygen produces 0.501g of CO2 and 0.103g of H2O. What is the empirical formula of
the acid? Given that another experiment has shown that the molar mass of the acid is 90.04g/mol, what is its
molecular formula?
#30. Dianabol is one of the anabolic steroids that has been used by some athletes to increase the size and
strength of their muscles. It is similar to the male hormone testosterone. Some studies indicate that the desired
effects of the drug are minimal, and the side effects, which include sterility and increased risk of liver cancer and
heart disease, keep most people from using it. The molecular formula of Dianabol, which consists of carbon,
hydrogen, and oxygen, can be determined using the data from two different experiments. In the first experiment,
14.765 g of Dianabol is burned, and 43.257 g CO2 and 12.395 g H2O are formed. In the second experiment, the
molecular mass of Dianabol is found to be 300.44. What is the molecular formula for Dianabol?
WORKSHEET #1
1. If you have a ring that contains 1.94 g of gold, how many atoms of gold are there in the ring?
2. Chlorine gas is a toxic gas that combines with sodium metal to produce table salt. If 12.5 L of Cl2 are used in this
reaction, how many atoms of Cl does this represent? (assume STP)
3. How many carbon atoms contain the same amount of mass as one molybdenum atom?
4. Dioxin is a powerful poison, and a by-product of the paper-bleaching process. How many moles of dioxin,
C12H4Cl4O2, are in 100.0 grams of dioxin? How many molecules?
5. Aspartame, C14H18N2O5, is the artificial sweetener that is 160 time sweeter than sucrose (table sugar) when
dissolved in water. Calculate the percent composition, by mass, of aspartame.
6. Cocaine has the following composition by mass: 67.30 % carbon, 6.93% hydrogen, 21.15% oxygen and 4.62 %
nitrogen. What is the empirical formula for cocaine?
7. Combustion of 0.5707 mg of a hydrocarbon (containing only hydrogen and carbon) produces 1.790 mg of CO2
and some water. What is the empirical formula of the hydrocarbon?
C?H? + O2 → CO2 +H20
8. A pure gas, containing only carbon and hydrogen, was found to be 85.63% carbon by mass. Its density is 2.50
g/L at STP. What is its molecular formula?
9. Air consist s of approximately 80% nitrogen and 20% oxygen, by volume. What is the mass of oxygen in 350 mL
of air at STP?
10. Oxalic acid is a compound used in cosmetics and paints. A 0.725 g sample of oxalic acid was found to contain
0.194 g of carbon, 0.016 g of hydrogen, and 0.516 g of oxygen. The molar mass of oxalic acid is 90.04 g/mol. What
is the molecular formula of oxalic acid?
CH7 WS1:
1. 5.93 x 1021
2. 6.72 x 1023
3. 7.99
4. 0.311 & 1.87 x 1023
5. 571.%, 6.1%, 9.5% & 27.2%
6. C17H21O4N
7. CH2
8. C4H8
9. 0.10
10. C2H2O4
WORKSHEET #2
1. Determine the number of representative particles in 2.55 x 10-4 moles of potassium cyanide (KCN), a
deadly poison.
2. Aluminum metal is produced by passing an electric current through a solution of aluminum oxide
dissolved in molten cryolite (Na3AlF6). Calculate the molar masses of aluminum oxide and Na3AlF6.
3. Juglone, a dye known for centuries, is produced from the husks of black walnuts. It is also a natural
herbicide (weed killer) that kills off competitive plants around the black walnut tree but does not affect grass
and other noncompetitive plants. The formula for juglone is C10H6O3.
a. Calculate the molar mass of juglone.
b. A sample of 1.56 x 10-2 g of pure juglone was extracted from black walnut husks. How many moles of
juglone does this sample represent?
4. Oxygen is required for metabolic combustion of foods. Calculate the number of atoms in 38.0g of oxygen
gas, the amount absorbed from the lungs at rest in about 15 minutes.
5. A 0.519g sample of gas is found to have a volume of 2.00 x 102 mL at STP. What is the molar mass of this
gas?
6. Propane (C3H8) is widely used in liquid form as a fuel for barbecue grills and camp stoves. For 75.3g of
propane, calculate the moles of carbon.
7. The first binary compounds containing a noble gas element were prepared at the Argonne National
Laboratories near Chicago in 1962. The first compound prepared was XeF4. Two other xenon fluorides,
XeF2 and XeF6 are also known. Calculate the mass percent of fluorine in each of these three compounds.
8. What is the density of N2O gas (laughing gas) at STP?
9. Determine the percent composition of chromium(III) oxide (Cr2O3).
10. What is the empirical formula of a compound that is 3.05% carbon, 0.26% hydrogen and 96.69% iodine?
11. Vitamin C (ascorbic acid) contains the elements carbon, hydrogen, and oxygen. It is known to contain
40.9% carbon and 4.58% hydrogen by mass. The molar mass of Vitamin C has been found to be 180.
g/mol. What is the molecular formula for Vitamin C?
12. Menthol, a strong-smelling substance used in cough drops, is a compound of carbon, hydrogen, and
oxygen. When 0.1595g of menthol was subjected to combustion analysis, it produced 0.449g of CO2 and
0.184g of H2O. The molar mass of menthol is 156.3g. What is its molecular formula?
CH7 WS2:
1. 1.54 x 1020
2. 102.0 & 210.0
3a. 174.0
3b. 8.97 x 10-5
4. 1.43 x 1024
5. 58.1
6. 5.13
7. 22.4% , 36.7% & 46.5%
8. 1.96
9. 68.4% & 31.6%
10. CHI3
11.C6H8O6
12. C10H20O
13. CH2
Review
1. How many grams are there in one mole of sulfuric acid (H2SO4)?
2. What is the molar mass of C6H5COOH?
3. How many grams of iron are there in 34.77 moles of iron?
4. How many molecules of water are there in 0.034 grams of water?
5. How many atoms of nitrogen are there in 35.0 moles of (NH4)2SO4?
6. What is the mass in grams of 1.000 x 1012 (1.000 trillion) atoms of gold?
7. How many grams of oxygen are there in 43.6 grams of CaCO3?
8. How many moles are there in 3.493 grams of lye, NaOH?
9. Calculate the % P in Ca3(PO4)2.
10. Analysis of a compound shows that the compound contains 26.67% S, 53.33% O, and 20.00% Mg. Determine
its simplest formula.
11. What is the empirical formula of a compound having the following composition: 38.76% Cl and 61.24% O?
12. Combustion of 6.38 g of ethylene glycol gives 9.06 g carbon dioxide and 5.58 g water. The compound contains
only C, H, and O. What is the empirical formula of ethylene glycol?
13. Combustion of 5.23 g of phenol yields 14.67 g carbon dioxide and 3.01g water. Phenol contains only C, H, and
O. What is the percentage of each element and what is the empirical formula of phenol?
14. Aniline consists of C, H, and N. Combustion of 9.71 g of aniline
yields 6.63 g water and 1.46 g nitrogen. What is the empirical
formula of aniline? The molar mass of aniline is 93.0g/mol.
What is the molecular formula of aniline?
Answers to Review!
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98.09g
122.13g/mol
1942 g
1.1 x 1021 molecules
4.21 x 1025 atoms N
3.272 x 10-10 g
20.9 g
0.08730 mol
20.00%
MgSO4
Cl2O7
CH3O
C6H6O 76.5%C, 6.5%H, 17.0%O
C6H7N for both emp. & mol. formulas