Assessment
Ch. 9 Practice Test
Chapter: Stoichiometry
In the space provided, write the letter of the term or phrase that best completes
each statement or best answers each question.
_____ 1. A balanced chemical equation allows one to determine the
a. mole ratio of any two substances in the reaction.
b. energy released in the reaction.
c. electron configuration of all elements in the reaction.
d. mechanism involved in the reaction.
_____ 2. The coefficients in a chemical equation represent the
a. masses, in grams, of all reactants and products.
b. relative numbers of moles of reactants and products.
c. number of atoms in each compound in a reaction.
d. number of valence electrons involved in the reaction.
_____ 3. To determine the limiting reactant in a chemical reaction involving
known masses of the two reactants, which of the following would be
most useful?
a. determining the masses of 100 mol of each reactant
b. determining the molar masses of the products
c. calculating bond energies
d. calculating the mass of a single product formed from each reactant
_____ 4. How many mole ratios can be correctly obtained from the chemical
equation 2Al2O3(l) → 4Al(s) + 3O2(g)
a. 3
b. 4
c. 6
d. 8
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Chapter Test
Chapter Test A, continued
_____ 5. In the equation 2Al2O3 → 4Al + 3O2, what is the mole ratio of
aluminum to oxygen?
a. 10:6
b. 3:4
c. 2:3
d. 4:3
_____ 6. Which of the following mathematical expressions correctly states the
relationship among percentage yield, actual yield, and theoretical
yield?
percentage yield
a. actual yield =
× 100
theoretical yield
actual yield
b. percentage yield =
× 100
theoretical yield
actual yield
c. theoretical yield =
× 100
percentage yield
d. Both (b) and (c)
_____ 7. The participation of reactants in a chemical reaction is restricted by the
a. limiting reactant.
b. limiting product.
c. excess reactant.
d. excess product.
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Chapter Test
Chapter Test A, continued
_____ 8. For the equation 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.
_____ 9. For a chemical reaction, percentage yield represents the
a. efficiency.
b. speed.
c. individual steps.
d. rate.
_____ 10. 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)
_____ 11. 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. temperature of the reaction
d. particles no longer reacting with each other
_____ 12. 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.
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Chapter Test
Chapter Test A, continued
_____ 13. In the reaction represented by the equation
CH4(g) + 2O2(g) → CO4(g) + 2H2O(g), a mass of 125 g CH4 is reacted
with excess oxygen. The expression
1 mol CH 4 2 mol H 2 O 18.02 g H 2 O
×
×
16.05 g CH 4 1 mol CH 4 1 mol H 2 O
is used to calculate the
a. mass of oxygen reacted.
b. mass of carbon dioxide produced.
c. mass of water produced.
d. None of the above
125 g CH 4 ×
_____ 14. What is the mole ratio of H2O to H3PO4 in the following chemical
equation?
P4O10 + 6H2O → 4H3PO4
a. 4 to 6
b. 1 to 6
c. 3 to 2
d. 2 to 3
_____ 15. 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.
_____ 16. In the formation of silicon carbide represented 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
Chapter Test A, continued
_____ 17. For the reaction represented by the equation SO3 + H2O → H2SO4,
what is the percentage yield if 500. g of sulfur trioxide react with
excess water to produce 575 g of sulfuric acid?
Element
Hydrogen
Oxygen
Molar mass
1.01 g/mol
16.00 g/mol
Sulfur
32.07 g/mol
a.
b.
c.
d.
82.7%
88.3%
91.2%
93.9%
_____ 18. If the percentage yield for the reaction represented by the following
equation is calculated to be 75.3%, what mass of Al is expected from
the reaction of 52.5 g of Al2O3?
2Al2O3(l) → 4Al(s) + 3O2(g)
Element
Aluminum
Oxygen
a.
b.
c.
d.
Molar mass
26.98 g/mol
16.00 g/mol
20.9 g Al
42.5 g Al
64.0 g Al
96.0 g Al
_____ 19. Ozone, O3, is produced in automobile exhaust by the reaction
represented by the equation
NO2(g) + O2(g) + NO(g) + O3(g)
What mass of ozone is predicted to form from the reaction of 2.0 g NO2
in a car’s exhaust and excess oxygen?
Element
Nitrogen
Oxygen
a.
b.
c.
d.
Molar mass
14.01 g/mol
16.00 g/mol
1.1 g O3
1.8 g O3
2.1 g O3
4.2 g O3
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Chapter Test