ANSWER KEY
Chemistry CPA Unit 6: Chemical Quantities
Test Study Guide
Test Date(s): Your test will be taken in two parts:
1. Written Exam: Tuesday, April 1
2. Lab Practical: Wednesday, April 2
Main Ideas for Unit 6:

Define the mole as a counting number

Relate counting particles to weighing samples of substances

Calculate the percent composition of atoms of elements within substances

Solve stoichiometric problems using molar mass (converting between
grams and moles)

Determine mole ratios from balanced chemical equations

Determine the limiting reactant of a chemical reaction based on mole
ratios
Unit 6 Materials to Review:

Green Notes Packet

Purple Assignment Packet

Coral Lab Packet

Do-Quizzes and Exit Passes

Graded Quizzes
Unit 6 Equations and Calculations:

Molar Mass

Percent Composition

Moles  Grams

Grams  Moles

Comparing Mole Ratios

Percent Yield
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
1
ANSWER KEY
Define the following terms (SEE TEXTBOOK)
1. Mole
2. Avagadro’s
Number
3. Molar Mass
4. Stoichiometry
5. Percent Yield
6. Theoretical
Yield
7. What is the purpose of the mole? Why do we need it?
To be able to correctly work with microscopic atoms at the macroscopic
level in the lab.
8. The mole has two different equivalent statements/definitions. What are
they, and which one is practical and necessary for lab work?

1 mole = 6.02x1023 particles

1 mole = molar mass of a substance (most practical for lab work)
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
2
ANSWER KEY
9. Find the molar mass of the following substances. The first two types
are done for you as a model. SHOW ALL WORK!!
CaCl2
Silver nitrate
Ca: 1 X 40.08 = 40.08
1x107.87=107.87
Cl: 2 x 35.45 = 70.90
Ag1+
= 110.98 g
(NO3)1-
Ag:
N: 1 x 14.01=
14.01
= AgNO3
O: 3 x 16.00 =
48.00
= 169.88
g
C2H4O2
Calcium hydroxide
Ca(OH)2
60.06 g
74.1 g
(NH4)2CO3
sodium phosphate
96.1 g
Na3PO4
163.94 g
Fe3(PO4)2
diboron hexahydride
357.49 g
B2H6
27.68 g
Zn(C2H3O2)2
sulfur hexachloride
183.43 g
SCl6
244.76 g
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
Find the percent composition of each element in the compounds below.
10. Silver perchlorate, AgClO4
%Ag=___52.03%_______
%Cl= ___17.10%___
%O= ____30.87%______
MM = 207.32 g
________________________________________________________________
11. Barium acetate, Ba(C2H3O2)2
%Ba = 53.78%
%C = 18.79%
%H = 2.37%
%O = 25.06%
MM = 255.39 g
________________________________________________________________
12. Acetone, C3H6O
%C =62.00%
%H =10.44%
%O = 27.56%
MM = 58.06 g
________________________________________________________________
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
For # 13-16, convert the following quantities from grams to moles. Use the
example below to help you:
“How many moles are in 98.3 grams of aluminum hydroxide, Al(OH)3?”
Step 1: Find the molar mass.
Al(OH)3 is 26.98 + (3 x 16.00) + (3 x 1.01) = 78.01 g/ mole
Step 2: Set up the equation and solve
98.3 grams x
1 mole____ = 1.2601 moles Al(OH)3 = 1.26 moles
78.01 grams
13. How many moles are there in 12.3 grams of carbon dioxide? 0.27 mol
14. How many moles are there in 89 grams of Pb(C2H3O2)4? 0.20 mol
15. How many moles are there in 110 grams of sodium bicarbonate?
1.31 mol
16. How many moles are there in 98.3 grams of aluminum hydroxide,
Al(OH)3? 1.26 mol
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
For # 17-20, convert the following quantities from moles to grams. Use the
example below to help you:
“How many grams are in 4.5 moles of sodium fluoride, NaF?”
Step 1: Find the molar mass of NaF: 22.99 + 19.00 = 41.99 g/ mole
Step 2: Set up the equation and solve
4.5 moles x 41.99 grams
1 mole
=
188.955 g NaF = 190 g NaF
17. How many grams are in 0.02 moles of beryllium iodide?
BeI2, 5.35 g
18. How many grams are in 5.6 moles of C6H6? 437.14 g
19. How many grams are in 1.2 moles of (NH4)3PO3? 159.74 g
20. How many grams are in 5.4 moles of potassium sulfate? K2SO4, 941.00
g
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
Stoichiometry – Mole Ratios
21. Zn + 2HCl  ZnCl2 + H2
A. How many moles of Zn are needed to completely react with 2 moles of
HCl? 1 mol
B. How many moles of H2 are produced with 1 mole of Zn? 1 mol
C. How many moles of Zn are needed to completely react with 4 moles of
HCl? 2 mol
22. 2 Ag2O  4 Ag + O2
A. How many moles of oxygen are produced by the decomposition of 2
moles of Ag2O? 1 mol
B. How many moles of oxygen are produced by the decomposition of 4
moles of Ag2O? 2 mol
C. How many moles of Ag are produced by the decomposition of 4 moles
of Ag2O? 8 mol
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
23. 2NaBr +
CaF2

2NaF +
CaBr2
A. Balance the reaction.
B. For every one mole of CaF2, how many moles of NaBr are needed?
2 mol
C. How many moles of NaF are produced from the reaction of 4 moles of
NaBr?
4 mol
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
Stoichiometry - Percent Yield
24. Balance the following equation:
2KClO3

2KCl +
3 O2
A. For every 2 moles of KClO3, ____2___ moles of KCl should be produced.
B. For every 2 moles of KClO3, ___3_____ moles of O2 should be produced.
C. For every 4 moles of KClO3, __3______ moles of O2 should be produced.
25. Lab Scenario The above decomposition reaction was completed in the lab using 245.1 g
KClO3. Use the steps below to find the mole ratio between KClO3 and O2.
A. Find the molar mass of KClO3. 122.55 g
B. Convert the amount of KClO3 used in the lab (245.1 g KClO3) to moles of
KClO3. 2 mol
C. After the reaction was completed, 90 grams of O2 were produced and
collected. Convert this to moles of O2 2.81 mol
D.
Determine the mole ratio of KClO3 to O2 from the lab data. This would be
your answer from B and C written as a ratio. 2 mol KClO3 : 2.81 mol O2
E. Compare your ratio from D to the ratio in the balanced equation (answer to
#2). Determine the percent yield.
% yield =
Actual moles of O2 x 100
Theoretical # of moles O2
= 93.67%
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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ANSWER KEY
26. Stoichiometry – Limiting Reagent
The following chemical reaction was performed:
3H2 
N2 +
2NH3
A. Balance the chemical equation.
B. 7 grams of N2 were reacted with 0.5 grams of H2. Fill in the information
below to find out which reactant was the limiting reactant:
1. How many moles are in 7 grams of N2? 0.25 mol
2. How many moles are in 0.5 grams of H2? .25 mol
3. What is the mole ratio of N2:H2 according to the balanced chemical
equation?
__1__ mol N2 : __3__ mol H2
4. What is the mole ratio of N2:H2 according to the calculations you did
for 1 and 2?
__0.25__ mol N2 : __0.25__ mol H2
5. Which must be the limiting reactant, N2 or H2? Explain why using
your answers from 3 & 4.
H2 is the limiting reactant
Unit 6 Test Study Guide
Callahan, Pengitore & Ricafort - 2014
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