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Assessment
Chapter Test
Stoichiometry
In the space provided, write the letter of the term or phrase that best completes
each statement or best answers each question.
______ 1. For the reaction SO3 H2O £ H2SO4, calculate the percentage yield if
500. g of sulfur trioxide react with excess water to produce 575 g of
sulfuric acid.
a. 82.7%
b. 88.3%
c. 91.2%
d. 93.9%
______ 2. In the reaction 2Al2O3 £ 4Al 3O2, what is the mole ratio of aluminum to oxygen?
a. 10:6
b. 3:4
c. 2:3
d. 4:3
______ 3. Fewer steps are required to solve stoichiometry problems when the
reactant is given in
a. grams and the product is sought in grams.
b. moles and the product is sought in moles.
c. grams and the product is sought in liters.
d. liters and the product is sought in number of atoms.
______ 4. Which of the following mathematical expressions correctly states the
relationship among percentage yield, actual yield, and theoretical
yield?
percentage yield
i. actual yield 100
theoretical yield
actual yield
ii. percentage yield 100
theoretical yield
actual yield
iii. theoretical yield 100
percentage yield
a. i
b. ii
c. iii
d. Both (b) and (c)
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Chapter Test continued
______ 5. The participation of other reactants in a chemical reaction is restricted
by the
a. limiting reactant.
b. limiting product.
c. excess reactant.
d. excess product.
______ 6. Which of the following expressions is not a legitimate conversion
factor?
1 mol
a. 6.022 1023 atoms
28.02 g N
b. 2
1 mol N2
1gC
c. 6.022 1023 atoms C
2.02 g H
d. 2
1 mol H2
______ 7. For the reaction P4(s) 5O2(g) £ P4O10(s), if 3 mol of phosphorus
react with 10 mol of oxygen, the theoretical yield of phosphorus(V)
oxide will be
a. 1 mol.
b. 2 mol.
c. 3 mol.
d. 10 mol.
______ 8. When a chemical reaction is performed in industry, the
is often chosen as the excess reagent.
a. least expensive and most abundant
b. most expensive and least abundant
c. least expensive and least abundant
d. most expensive and most abundant
chemical
______ 9. A convenient stoichiometric measurement for an evolving gas is
a. volume.
b. mass.
c. atoms.
d. molecules.
______10. Percent yield represents the
a. efficiency
b. speed
c. individual steps
d. rate
of a chemical reaction.
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Chapter Test continued
______11. The pollution produced by combustion engines can be partially
controlled by which of the following?
a. the use of a catalytic converter
b. adjusting the contents of the gasoline
c. having a well-tuned engine
d. All of the above
______12. The limiting reactant of a reaction can be used to calculate the
a. actual yield.
b. theoretical yield.
c. experimental yield.
d. Both (a) and (c)
______13. The excess reactant when starting a gasoline (isooctane) engine is
a. C8H18.
b. CO2.
c. O2.
d. H2O.
______14. Which of the following factors does not affect the actual yield of a
reaction?
a. side reactions that compete with the main reaction
b. reactions that are the reverse of the main reaction
c. a mixture of reactants and products
d. particles no longer reacting with each other
______15. If the percentage yield for a chemical reaction is 80.0%, the
a. actual yield is 80.0 g for every theoretical yield of 100. g.
b. theoretical yield is 80.0 g for every actual yield of 100. g.
c. actual yield is 80 times as much as the theoretical yield.
d. theoretical yield is 80 times as much as the actual yield.
______16. In the reaction, CH4(g) 2O2(g) £ CO2(g) 2H2O(g), a mass of 125 g
CH4 is reacted with excess oxygen. The following expression
1 mol CH4
2 mol H2O 18.02 g H2O
125 g CH4 16.05 g CH4 1 mol CH4
1 mol H2O
calculates the
a. mass of oxygen reacted.
b. mass of carbon dioxide produced.
c. mass of water produced.
d. None of the above
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Chapter Test continued
______ 17. How many mole ratios can be correctly obtained from the following
chemical equation?
P4O10 6H2O £ 4H3PO4
a.
b.
c.
d.
1
3
6
9
______18. In most chemical reactions, the amount of product obtained is
a. equal to the theoretical yield.
b. less than the theoretical yield.
c. more than the theoretical yield.
d. more than the percentage yield.
1
______19. The expression mass has the unit
molar mass
a. g/mol.
b. mol/g.
c. g.
d. mol.
______20. In the formation of silicon carbide, given by the chemical equation,
SiO2(s) 3C(s) £ SiC(s) 2CO(g), 8 mol of each reactant are available for the reaction. What substance is the excess reactant?
a. SiO2(s)
b. C(s)
c. SiC(s)
d. CO(g)
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Chapter Test continued
Answer the following items in the spaces provided.
21. Explain why the limiting reactant may not be used completely when the
percentage yield for a reaction is 70%.
22. Why should you use moles in stoichiometric problems?
23. The equation for the burning of gasoline shows that carbon dioxide, water,
and energy are the only products of combustion. Yet burning gasoline in car
engines causes air pollution. What information not revealed by the equation
accounts for the pollutants?
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Chapter Test continued
Answer each of the following problems in the spaces provided.
24. What mass in grams of potassium chloride is produced if 100. g of potassium
chlorate decompose according to the following equation?
2KClO3(s) –heat
–£ 2KCl(s) 3O2(g)
25. A research chemist designing an air bag is looking at carbon dioxide as a
possible gas for bag inflation. One of the reactions the chemist is working
with is the following.
MgCO3(s) £ MgO(s) CO2(g)
How many grams of magnesium carbonate are needed to produce enough
carbon dioxide to inflate an air bag to a volume of 65.0 L? Use 1.961 g/L as the
density of carbon dioxide gas.
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TEACHER RESOURCE PAGE
Answer Key
Quiz—Section: Calculating
Quantities in Reactions
1.
2.
3.
4.
5.
d
c
c
d
b
6.
7.
8.
9.
10.
21. Thirty percent of the expected product
is not produced. Therefore, thirty percent of the limiting reactant must be
part of reverse or side reactions.
22. Moles are used because the coefficients in a balanced equation show the
number of moles of reactants and
products in the chemical reaction.
23. The equation does not show other
components of air, such as nitrogen
and organic compounds. It also does
not show impurities in gasoline, such
as compounds of nitrogen and sulfur.
During combustion, these substances
are also oxidized, producing pollutants
such as nitrogen, sulfur oxides, and
hydrocarbons. In addition, the equation does not show that incomplete
combustion can occur, in which case
carbon monoxide is also produced.
1 mol KClO3
24. 100. g KClO3 122.5 g KClO3
74.55 g KCl
2 mol KCl
1 mol KCl
1 mol KClO3
c
a
c
c
c
Quiz—Section: Limiting
Reactants and Percentage
Yield
1.
2.
3.
4.
5.
b
d
c
c
b
6.
7.
8.
9.
10.
c
a
d
d
b
Quiz—Section:
Stoichiometry and Cars
1.
2.
3.
4.
5.
b
c
c
c
c
6.
7.
8.
9.
10.
d
b
a
b
b
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
d
b
a
d
a
c
c
b
d
a
60.8 g KCl
1.961 g CO
1 L CO2
1 mol CO2
1 mol MgCO
3
44.01 g CO2
1 mol CO2
84.31 g MgCO
3 244 g MgCO3
1 mol MgCO3
25. 65.0 L CO2 2
Chapter Test
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
d
d
b
d
a
c
b
a
a
a
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Holt Chemistry
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Stoichiometry