Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
115
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 11
Percent yield tells you how efficient a chemical reaction is in producing the desired product.
Example Problem 11-6
Calculating Percent Yield
Aspirin (C 9 H 8 O 4 ) can be made from salicylic acid (C 7 H 6 O 3 ) and
acetic anhydride (C 4 H 6 O 3 ). Suppose you mix 13.2 g of salicylic acid
with an excess of acetic anhydride and obtain 5.9 g of aspirin and
some water. Calculate the percent yield of aspirin in this reaction.
Write the balanced equation.
2C 7 H 6 O 3 (s) ϩ C 4 H 6 O 3 (l) 0 2C 9 H 8 O 4 (s) ϩ H 2 O(l)
Calculate the theoretical yield. Salicylic acid is the limiting reactant.
13.2 g C 7 H 6 O 3 ϫ
ϭ 0.0956 mol C 7 H 6 O 3
0.0956 mol C 7 H 6 O 3 ϫ
ϭ 0.0956 mol C 9 H 8 O 4
0.0956 mol C 9 H 8 O 4 ϫ
ϭ 17.2 g C 9 H 8 O 4
Calculate the percent yield.
ϫ 100 ϭ 34%
Practice Problems
11. Calculate the percent yield for each chemical reaction based on
the data provided.
a. theoretical yield: 25 g; actual yield: 20 g
b. theoretical yield: 55 g; actual yield: 42 g
c. theoretical yield: 5.2 g; actual yield: 4.9 g
12. Calculate the actual yield for each chemical reaction based on
the data provided.
a. theoretical yield: 20 g; percent yield: 95%
b. theoretical yield: 75 g; percent yield: 88%
c. theoretical yield: 9.2 g; percent yield: 62%
5.9 g C 9 H 8 O 4
ᎏᎏ
17.2 g C 9 H 8 O 4
180.2 g C 9 H 8 O 4
ᎏᎏ
1 mol C 9 H 8 O 4
2 mol C 9 H 8 O 4
ᎏᎏ
2 mol C 7 H 6 O 3
1 mol C 7 H 6 O 3
ᎏᎏ
138.1 g C 7 H 6 O 3