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Chapter 8: Quantities in Chemical Reactions – Study Guide
*Do not forget about the extra resources available to help you study and prepare for this test!
 Textbook pages 273 – 283
 Mastering Chemistry Study Area: http://www.pearsonmylabandmastering.com/northamerica/
 Miss Marnik’s Website: http://www.northallegheny.org/Page/16665
 Labs, problem packets, and homework assignments
Section 1 – Defining Stoichiometry: (text pages 250-253)
Need to be able to:
 Describe the types of relationships indicated by a balanced chemical equation.
 State the mole ratios from a balanced chemical equation.
Practice Problems:
1. For each statement, write true or false.
a. _______________ The study of the quantitative relationships between the amounts of
reactants used and the amounts of products formed by a chemical reaction is called
stoichiometry.
b. _______________ Stoichiometry is based on the law of conservation of mass.
c. _______________ In any chemical reaction, the mass of the products is less than the mass of
the reactants.
d. _______________ The coefficients in a chemical equation represent not only the number of
individual particles but also the number of moles of particles.
e. _______________ The mass of each reactant and product is related to its coefficient in the
balanced chemical equation for the reaction by its molar mass.
2. Complete the table below, using information represented in the chemical equation for the combustion
of methanol.
2CH3OH(l)  3O2 (g) → 2CO2(g)  4H2O(g)
Substance
Number of
Molecules
Number of
Moles (mol)
Molar Mass (g/mol)
Mass (g)
Methanol
Oxygen gas
Carbon dioxide
Water
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3. Balance the following chemical reaction and then answer the questions:
Na(s) +
Fe2O3(s) 
Na2O(s) +
Fe(s)
a. Predict the number of mole ratios for this reaction._____________
b. What are the mole ratios for this reaction?
c. What is the mole ratio relating sodium to iron? _______________________
d. What is the mole ratio relating iron (III) oxide to iron?_______________________
e. Which mole ratio has the largest value?_______________________
Section 2 – Stoichiometric Calculations: (text pages 251-257)
Need to be able to:
 List the sequence of steps used in solving stoichiometric problems.
 Solve stoichiometric problems.
Practice Problems
4. The reaction of sodium peroxide and water produces sodium hydroxide and oxygen gas. Use this
reaction for questions a-d.
Na2O2(s) 
H2O(l) →
NaOH(s) 
O2(g)
a. How many moles of sodium hydroxide are produced when 1.00 mol sodium peroxide reacts
with water?
b. How many moles of oxygen gas are produced when 0.500 mol Na2O2 reacts with water?
Honors Chemistry
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c. How many moles of sodium peroxide are needed to produce 1.00 mol sodium hydroxide?
d. How many moles of water are required to produce 2.15 mol oxygen gas in this reaction?
5. In a blast furnace, iron and carbon monoxide are produced from the reaction of iron(III) oxide and
carbon. How many grams of iron are formed when 150.25 g iron(III) oxide reacts with an excess of
carbon?
6. Solid sulfur tetrafluoride and water react to form sulfur dioxide and an aqueous solution of hydrogen
fluoride. How many grams of water are necessary for 20.40 g sulfur tetrafluoride to react completely?
7. How many moles of oxygen are needed for 500.00 g of iron metal to react completely in a combustion
reaction?
Fe(s) +
O2(g) 
Fe2O3(s)
8. How many grams of carbon dioxide are produced if 4.34 moles of propane (C3H8) are combusted in a
space heater?
C3H8(l) +
Honors Chemistry
O2(g) 
CO2(g) +
H2O(g)
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Section 3 – Limiting Reactants and Percent Yield: (text pages 257-264)
Need to be able to:
 Identify the limiting reactant in a chemical equation.
 Identify the excess reactant, and calculate the amount remaining after the reaction is complete.
 Calculate the mass of a product when the amounts of more than one reactant are given.
 Calculate the theoretical yield of a chemical reaction from data.
 Determine the percent yield for a chemical reaction.
Practice Problems:
9. Consider the reaction:
2Na(s) + F2(g)  2NaF(s)
If you begin with 4.8 mol of sodium and 2.6 mol of fluorine, what is the limiting reactant and
theoretical yield of NaF in moles?
10. Ammonia can be synthesized by this reaction:
3H2(g) + N2(g)  2NH3(g)
What maximum amount of ammonia in grams can be synthesized from 25.2 g of N2 and 8.42 g of H2?
11. The reaction used to obtain iron from iron ore is:
Fe2O3(s) + 3CO(g)  2Fe(s) + 3CO2(g)
The reaction of 185 g of Fe2O3 with 95.3 g of CO produces 87.4 g of Fe. Determine the limiting reactant,
theoretical yield, and percent yield.
12. Urea (CH4N2O), a common fertilizer, can be synthesized using the following reaction:
2NH3(aq) + CO2(aq)  CH4N2O(aq) + H2O(l)
An industrial synthesis of urea produces 87,500 g of urea upon reaction with 68,200 g of ammonia
with 105,000 g of carbon dioxide. Determine the limiting reactant, theoretical yield of urea, and
percent yield for the reaction.
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