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116 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 11
13. In an experiment, 10.0 g of magnesium reacted with excess
hydrochloric acid forming magnesium chloride.
Mg(s) ϩ 2HCl(aq) 0 MgCl 2 (aq) ϩ H 2 (g)
At the completion of the reaction, 29.5 g of magnesium chloride was produced. Calculate the theoretical yield and the
percent yield.
Percent yield is important in the calculation of overall cost effectiveness in industrial processes. Manufacturers must reduce the cost of
making products to the lowest level possible. For example, sulfuric
acid (H 2 SO 4 ) is a raw material for many products, including fertilizers, detergents, pigments, and textiles. The cost of sulfuric acid
affects the cost of many consumer items that use sulfuric acid as a
raw material.
The manufacture of sulfuric acid is sometimes achieved using a
two-step process called the contact process. The two steps are as
follows.
S 8 (s) ϩ 8O 2 (g) 0 8SO 2 (g)
2SO 2 (g) ϩ O 2 (g) 0 2SO 3 (g)
The last step results in sulfuric acid as the product.
SO 3 (g) ϩ H 2 O(l) 0 H 2 SO 4 (aq)
The first step produces almost 100 percent yield. The second step
will also produce a high yield if a catalyst is used. A catalyst is a
substance that speeds up a chemical reaction but is not used up in
the chemical reaction and does not appear in the chemical equation.
Chapter 11 Review
14. What is stoichiometry?
15. Write two questions that stoichiometry can help you answer
about the following chemical equation.
4HCl(aq) ϩ O 2 (g) 0 2H 2 O(l) ϩ 2Cl 2 (g)
16. Relate the law of conservation of mass to stoichiometry.
17. What is the difference between a limiting reactant and an
excess reactant?
116 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 11
13. In an experiment, 10.0 g of magnesium reacted with excess
hydrochloric acid forming magnesium chloride.
Mg(s) ϩ 2HCl(aq) 0 MgCl 2 (aq) ϩ H 2 (g)
At the completion of the reaction, 29.5 g of magnesium chloride was produced. Calculate the theoretical yield and the
percent yield.
Percent yield is important in the calculation of overall cost effectiveness in industrial processes. Manufacturers must reduce the cost of
making products to the lowest level possible. For example, sulfuric
acid (H 2 SO 4 ) is a raw material for many products, including fertilizers, detergents, pigments, and textiles. The cost of sulfuric acid
affects the cost of many consumer items that use sulfuric acid as a
raw material.
The manufacture of sulfuric acid is sometimes achieved using a
two-step process called the contact process. The two steps are as
follows.
S 8 (s) ϩ 8O 2 (g) 0 8SO 2 (g)
2SO 2 (g) ϩ O 2 (g) 0 2SO 3 (g)
The last step results in sulfuric acid as the product.
SO 3 (g) ϩ H 2 O(l) 0 H 2 SO 4 (aq)
The first step produces almost 100 percent yield. The second step
will also produce a high yield if a catalyst is used. A catalyst is a
substance that speeds up a chemical reaction but is not used up in
the chemical reaction and does not appear in the chemical equation.
Chapter 11 Review
14. What is stoichiometry?
15. Write two questions that stoichiometry can help you answer
about the following chemical equation.
4HCl(aq) ϩ O 2 (g) 0 2H 2 O(l) ϩ 2Cl 2 (g)
16. Relate the law of conservation of mass to stoichiometry.
17. What is the difference between a limiting reactant and an
excess reactant?