Download THE MOLE (a counting unit)……….Again!

Name:___________________________________________Period:______Date:____________
THE MOLE (a counting unit)……….Again!
Ö A mole represents a______________________________, much in the same way
that a dozen represents a set of twelve.
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1 dozen eggs = 12 eggs; 1 mol eggs = 6.022 × 1023 eggs
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1 dozen carbon atoms = 12 carbon atoms; 1 mol carbon atoms = 6.022 × 1023 carbon atoms
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The number “6.022 × 1023 ” is known as “___________________________________”.
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If you write out Avogadro’s number, it looks like this:
602,200,000,000,000,000,000,000
Ö Remember:
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1 mole of atoms = 6.02 × 1023 atoms
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1 mole of molecules = 6.02 × 1023 molecules
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1 mole of formula units = 6.02 × 1023 formula units
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1 mole of ions = 6.02 × 1023 ions
Ö Atomic Mass vs. Molar Mass:
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__________________________= the mass of ONE ATOM expressed in atomic mass units
(amu)
o Ex: Oxygen’ s atomic mass = 15.999 amu; this is the average mass of ____ oxygen atom
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___________________________= the mass of ONE MOLE of atoms, molecules, or formula
units expressed in grams
o Ex: Oxygen’s molar mass = 15.999 g; this is the mass of _______________ oxygen atoms
Atomic Mass vs. Molar Mass
Element & Symbol
Atomic Mass—Average mass of 1
Atom
Carbon (C)
12.0 amu
Helium (He)
4.00 amu
Molar Mass—Mass of 1 mole of
atoms (6.02 X 1023 atoms)
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ACIDS: You need to know these!
Hydrochloric Acid = ____________
Nitric Acid =_________________
Sulfuric Acid =_______________
Carbonic Acid = _________________
Phosphoric Acid =_____________
Acetic Acid = _____________________
I. CALCULATING MOLAR MASS:
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Find the molar mass of each of the following compounds:
1. Phosphoric Acid
2. Calcium Nitrate
3. Iron (III) Carbonate
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Molar Mass Homework #1-9 Below
•
Find the molar mass for the following compounds:
1) sulfuric acid
2) iron (II) bromide
3) manganese(II) phosphate
4) diphosphorous pentoxide
•
Answer the following questions based on your notes.
5) ___________________________ is the mass of ONE MOLE of atoms, molecules, or formula
units expressed in ___________________
6) _________________________ is the mass of ONE ATOM expressed in _______________
7) What is the numeric value of “the mole”? ______________________________
8) What does the mole measure? _______________________________________
9) The mole is also referred to as ____________________________ number.
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II. FINDING PERCENT COMPOSITION:
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____________________________= is the percent by mass of each element in the compound.
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The percent composition is ______________the same regardless of the size of the sample.
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Ex: H20 is ALWAYS 11.2 % hydrogen and 88.8% oxygen (by mass)
The percent composition of the elements in a compound adds up to _______.
Formula Used:
Molar Mass of the element in a compound
Total Molar Mass of the compound
Or think of it as:
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X 100
Part _ X 100
Whole
Steps:
1. Find molar mass of each element (parts)
2. Find the total molar mass of the compound (whole)
3.
Part
X 100
Whole
4. Evaluate your answer (percentages should add to approximately 100%)
Ex: Find the percent composition of aluminum sulfate.
NOTE: Therefore, a 100g sample of Al2(SO4)3 would contain ________g Al, _______g S, and _________g O
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% Composition Homework: # 1-4 Below
1. Find the percent composition of magnesium hydroxide.
2. Find the percent composition of calcium cyanide.
3. Find the percent composition of nickel (II) iodide.
4. Find the percent composition of copper (I) sulfide.
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III. CONVERSIONS BETWEEN GRAMS & MOLES
o KEY IDEA: It is important to know the following conversion: The molar mass of a compound or the
mass an element is equal to 1 mole of that compound or element.
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Ex: 1 mole of carbon is equal to 12 grams of carbon!
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Ex: ______________of water is equal to ______________(molar mass) of water
o Use a T-chart to convert from what you know to what you do not know. Use your conversion factors
so ________________cancel out!
Ö Ex #1: How many moles are represented by 11.5 g of magnesium hydroxide?
Ö Ex #2: How many grams of aluminum sulfide are present in 0.44 moles of aluminum sulfide?
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Grams & Moles Conversion Homework = #1-4 Below
1. How many grams of barium cyanide are present in 0.638 moles of barium cyanide?
2. How many moles of calcium bromide are present in 50.4 grams of calcium bromide?
3. How many grams of calcium hydroxide are present in 1.26 moles of calcium hydroxide?
4. How many moles of acetic acid are present in 86.2 grams of acetic acid?
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IV. CALCULATION of FORMULAS:
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2 types of formulas:
1. _____________________________________ (M.F.) = shows the types and numbers
of atoms combined in a single molecule.
o Ex: C6H12O6 (glucose)
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Actually has 24 atoms!
2. ______________________________________ (E.F.) = a chemical formula showing
the simplest whole number ratio of atoms in a compound.
o Ex: Reduce glucose C6H12O6 by dividing all the subscripts by 6 – the empirical
formula would be _________________
o In the chart below, fill in the empirical formula given the molecular formula:
Molecular Formula
Empirical Formula
H2O2
H2O
C8H16
C2H4
o Notice 2 things:
1. Some molecular formulas ___________ be reduced (H2O)
2. Several compounds can _______________the same E.F., but each
compound has its own _________________molecular formula
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WHY DO WE USE THE EMPIRICAL FORMULA IF IT CONTAINS LESS INFORMATION?
It is easier to experimentally determine the empirical formula of a compound than the
molecular formula. So the E.F. is usually found 1st as a step towards finding the
molecular formula.
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• Steps to finding an EMPIRICAL FORMULA:
1. The amount of each element should be listed in grams. If analysis of the compound is in
percent, convert to grams: assume a 100 g sample of the compound.
2. Convert grams of EACH element to moles (T-chart).
3. Divide moles of each element by the smallest number of moles.
4. Round each answer from “3” to the nearest whole number and write the empirical formula
using these numbers as subscripts.
* NOTE: ROUND ALL NUMBERS to 0.001
Ex #1: What is the empirical formula for a compound if a sample contains 0.9g of calcium and 1.6g of
chlorine?
Ex # 2: What is the empirical formula for a compound that is 40% C, 6.71% H, and 53.3% O?
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Empirical Formula Homework: #1-4 Below
1. Calculate the empirical formula of a compound that contains 1.67g of cerium, Ce, and 4.54g of iodine, I.
2. 2-Methylpropene is a compound used to make synthetic rubber. A sample of 2-methylpropene contains 0.566g C and
0.0933g H. Determine its empirical formula.
3. Determine the empirical formula of a compound containing 63.50% silver, 8.25% nitrogen, and 28.25% oxygen.
4. Freons are gaseous compounds used in refrigeration. A particular freon contains 9.93% C, 58.6% Cl, and 31.4% F by
mass. What is the empirical formula of this freon?
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• Steps to finding a MOLECULAR FORMULA
1. If it is not given, determine the empirical formula of the compound. (Follow all steps
necessary to determine an empirical formula)
2. Calculate molar mass of the empirical formula.
3. Divide the molar mass of the _____________________by the molar mass determined from
the___________________________________.
4. Round the answer to “3” to the nearest whole number and multiply all subscripts in the
empirical formula by this number.
Ex #1: What is the molecular formula of a substance that has an empirical formula of AgCO2 and a
molar mass of 304g/mol?
Ex #2: An unknown compound contains 85.64% carbon and 14.36% hydrogen. It has a molar mass
of 42.08 g/mol. Find its molecular formula.
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Molecular Formula Homework: #1-7 Below
1. The molar mass of benzene, an important industrial solvent, is 78.0g/mol and its empirical formula is CH. What is the
molecular formula for benzene?
2. What is the molecular formula of dichloroacetic acid, if the empirical formula is CHOCl and the molar mass of the acid is
129g/mol?
3. A compound used as an additive for gasoline to help prevent engine knock, shows the following percentage
composition: 24.27% C, 4.07% H, and 71.65% Cl. The molar mass is known to be 98.96 g/mol. Determine the empirical
formula and the molecular formula for this compound.
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4. Suppose a sample of cyclohexane contains 4.282 g of carbon and 0.718 g of hydrogen. The molar mass of
cyclohexane is 84.2 g/mol. Determine the molecular formula.
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Answer the following questions based on your notes.
5. The _____________________________________specifies the actual number of atoms of each element in
one molecule or formula unit of the substance.
6. The _____________________________________ for a compound is the formula with the smallest wholenumber ratio between elements.
7. What is the empirical formula for C10H8? __________________
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copper II sulfate pentahydrate
CuSO4● 5H2O
V. HYDRATES:
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Suppose an ionic substance is dissolved in water. The water can be
evaporated to leave the solid ionic compound. SOME ionic compounds,
however, will form solid crystals that incorporate
________________________(where the water molecules are weakly attracted to the ions in the
crystal structure).
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__________________________= an ionic compound containing water molecules incorporated
into its solid crystal structure
o In other words, a hydrate is a collection of ________________(negative ions),
_____________________(positive ions), and _____________________________
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_________________________________= the ionic compound that remains after the water has
been removed (usually by heating) from the hydrate
o Note: salt = ionic compound (usually an ionic compound that does not contain OH − ions)
•
The heating of a hydrate to produce an anhydrous salt can be illustrated as follows:
hydrate + heat → anhydrous salt + water
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Naming Hydrates & Writing Hydrate Formulas:
o Prefixes are used as coefficients in the following manner in the chemical formulas for
hydrates.
o The chemical formula for magnesium sulfate heptahydrate is ______________________
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7 moles of H2O are associated with every 1 mole of MgSO4.
o The chemical formula for zinc sulfate dihydrate is _____________________________
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2 moles of H2O are associated with every 1 mole of ZnSO4.
o What is the name of the following hydrate, FePO4 • 4H2O?
__________________________________________________________________
MOLAR MASS OF HYDRATES:
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When determining the molar mass of a hydrate, the molar mass of the associated water must be
included.
EX #1: Calculate the molar mass of calcium sulfate dihydrate.
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PERCENT COMPOSITION of HYDRATES:
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Steps:
1. Find molar mass of water.
2. Find the molar mass of the salt.
3. Add the mass of the water and the salt in order to get the total mass of the hydrate.
4.
Mass of Water (part) __ X 100
Mass of Hydrate (whole)
Ex: What percentage of water is found in sodium sulfide nonahydrate?
EMPIRICAL FORMULA of a HYDRATE:
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Steps:
1.
Identify what you know and what you do not know.
2.
All amounts should be listed in grams. If analysis is in percent, convert to grams:
assume a 100 g sample.
3.
Convert grams of anhydrous salt to moles.
4.
Convert grams of water to moles.
5.
Divide moles by the smallest number of moles.
6.
Round each answer from “5” to the nearest whole number and these numbers
become the COEFFICIENTS for the salt and water.
Ex: Suppose a hydrate contains 9.520 g barium iodide and 0.887g water. Determine the formula of
the hydrate.
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Hydrate Homework: #1-12
1. Determine the percentage of water in copper (II) sulfate pentahydrate.
2. Suppose a hydrate contains 0.391g Li2SiF6 and 0.0903g H20. Determine the formula of the hydrate.
3. Determine the percentage of water in sodium carbonate monohydrate.
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4. Suppose a hydrate contains 0.737g magnesium sulfate and 0.736g water. Determine the formula of the hydrate.
5. Suppose a hydrate contains 76.9% calcium sulfite and 23.1% water. Determine the formula of the hydrate.
6. Suppose a hydrate contains 89.2% barium bromide and 10.8% water. Determine the formula of the hydrate.
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7. The ____________________________ salt is the ionic compound that remains after the water has been
removed from the hydrate.
8. A _______________________ is an ionic compound containing water molecules incorporated into its solid
crystal structure.
9. How can water molecules be removed from a hydrate?
10. What is the formula for nickel II chloride hexahydrate? ______________________________
11. How many water molecules are present in the following hydrate: nickel II chloride hexahydrate? _______
12. Write the name of the following compound: MgCO3 • 5H20 _________________________________
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THE MOLE & MATH REVIEW WORKSHEET
1) Calculate the molar mass for the following:
a) Aluminum sulfate
b) Ammonium phosphate
2) Convert:
a) 6.38 moles of iron (II) phosphate to g
b) 5.49 moles of potassium iodide to g
c) 188 g calcium hydroxide to moles
d) 84.2 g potassium phosphate to moles
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3) Find the percent composition of zinc hydroxide.
4) Determine the percent of water in sodium sulfate decahydrate.
5) Determine the empirical formulas for the following two compounds that were analyzed and found to
contain the following:
a) 3.30 g magnesium, 21.7 g bromine
b) 40.23% potassium, 26.95% chromium, 32.81% oxygen
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6) A compound of aluminum and chlorine is composed of 9.00 g of aluminum for every 35.5 g of chlorine.
The molar mass of this compound is 267 g/mol. Determine the empirical formula and the molecular
formula.
7) A compound with a molar mass of 180.15 g/mol is found to be 40.00% carbon, 6.71% H, and 53.28%
oxygen. Determine the empirical formula and the molecular formula of the compound.
8) What is the formula for a hydrate that is 90.7% strontium oxalate and 9.30% water?
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9) What is the formula for a hydrate that is 433.5 grams of Mo2S5 and 66.5 grams of H2O?
10) The _________________________________ is the mass of one mole of atoms, molecules, or formula units
and is expressed in ____________________________________.
11) The __________________specifies the actual number of atoms of each element in one molecule or formula
unit of the substance.
12) ______________________________ is the numeric value of “the mole”.
13) The ____________________________ salt is the ionic compound that remains after the water has been
removed from the hydrate.
14) The ______________________ is the mass of one atom and is expressed in _______________________.
15) The ______________________ for a compound is the formula with the smallest whole-number ratio
between elements.
16) What does the mole measure?______________________________________________________
17) A _____________________ is an ionic solid with trapped water molecules.
18) What is the empirical formula for C6H8O6? _____________________________
19) The mole is also referred to as _____________________________ number.
20) How many water molecules are present in the following hydrate: barium hydroxide octahydrate? ___
21) Write the formulas for the following acids:
a) Carbonic acid ___________________________________
b) Sulfuric acid ___________________________________
c) Phosphoric acid ___________________________________
d) Nitric acid ___________________________________
e) Acetic acid ___________________________________
f) Hydrochloric acid ___________________________________
22) What is the formula for sodium acetate trihydrate? ______________________________
23) Write the name of the following compound: CoCl2 • 6H20 _________________________________
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Unit Learning Map (11 days):
Mole & Math
Mrs. Hostetter
Class: Academic Chemistry A - Grade 11
Unit Essential Question(s):
Optional
Instructional Tools:
How do you analyze and
solve chemistry math
problems?
Concept
Molar mass
Lesson Essential Questions:
How is molar mass
determined?
Vocabulary:
Mole
Atomic mass
Formula mass
Molar mass
Concept
Percent composition
Lesson Essential Questions:
How is percent
composition
determined?
Vocabulary:
Percent composition
Guided Notes
Lab Materials:
Chalk Lab
MgO Lab
Hydrate Lab
Concept
Concept
Conversions
Empirical and
molecular formulas
Lesson Essential Questions:
How are molar mass
and Avogadro’s
number used in
conversion?
Vocabulary:
Molar mass
Avogadro’s number
Lesson Essential Questions:
How are empirical and
molecular formulas
determined?
Vocabulary:
Empirical formula
Molecular formula
Hydrate
Anhydrous
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Math & Moles Vocabulary:
1) Mole = unit of measurement for an amount of a something; a counting unit
2) Atomic mass = the mass of one atom expressed in atomic mass units
3) Molar mass = the mass of one mole of atoms, molecules, or formula units expressed in grams
4) Percent Composition = is the percent by mass of each element in the compound
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Steps:
1. Find molar mass of each element (parts)
2. Find the total molar mass of the compound (whole)
3.
Part
X 100
Whole
4. Evaluate your answer (percentages should add to approximately 100%)
5) Avagadro’s number = 6.022 x 1023
6) Molecular formula (M.F.) = shows the types and numbers of atoms combined in a single molecule
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Steps to finding a MOLECULAR FORMULA
1. If it is not given, determine the empirical formula of the compound. (Follow all steps
necessary to determine an empirical formula)
2. Calculate molar mass of the empirical formula.
3. Divide the molar mass of the compound by the molar mass determined from the empirical
formula.
4. Round the answer to “3” to the nearest whole number and multiply all subscripts in the
empirical formula by this number.
7) Empirical formula (E.F.) = a chemical formula showing the simplest whole number ratio of atoms in a
compound
•
Steps to finding an EMPIRICAL FORMULA:
1. The amount of each element should be listed in grams. If analysis of the compound is in
percent, convert to grams: assume a 100 g sample of the compound.
2. Convert grams of EACH element to moles (T-chart).
3. Divide moles of each element by the smallest number of moles.
4. Round each answer from “3” to the nearest whole number and write the empirical formula
using these numbers as subscripts.
8) Hydrate = an ionic compound containing water molecules incorporated into its solid crystal structure
9) Anhydrous salt = the ionic compound that remains after the water has been removed (usually by heating)
from the hydrate
ACIDS: You need to know these!
Hydrochloric Acid = HCl
Nitric Acid = HNO3
Phosphoric Acid = H3PO4
Sulfuric Acid = H2SO4
Carbonic Acid = H2CO3
Acetic Acid = CH3COOH
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