Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
204 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 19
ions. To maintain balance, you must also add eight Cl Ϫ ions to the
left, where they join with the hydrogen ions.
K 2 Cr 2 O 7 (aq) ϩ 14HCl(aq) 0
2CrCl 3 (aq) ϩ 2KCl(aq) ϩ 3Cl 2 (g) ϩ 7H 2 O(l)
The chemical equation is balanced, with the state descriptions
restored. Note that no subscripts have been changed.
Practice Problems
6. Use the half-reaction method to balance these redox equations.
Start with step 2 of Example Problem 20-4 and leave the balanced equation in ionic form.
a. I 2 (s) ϩ H 2 SO 3 (aq) 0 I Ϫ (aq) ϩ HSO 4
Ϫ (aq)
b. Fe 2ϩ (aq) ϩ MnO 4
Ϫ (aq) 0 Fe 3ϩ (aq) ϩ Mn 2ϩ (aq)
c. Zn(s) ϩ Cr 2 O 7
2Ϫ (aq) 0 Zn 2ϩ (aq) ϩ Cr 3ϩ (aq)
d. IO 3
Ϫ (aq) ϩ I Ϫ (aq) 0 I 2 (s)
Chapter 19 Review
7. Which of these unbalanced equations do NOT represent redox
reactions? Explain your answer.
a. C 2 H 6 ϩ O 2 0 CO 2 ϩ H 2 O
b. BaCl 2 ϩ NaIO 3 0 Ba(IO 3 ) 2 ϩ NaCl
c. Al(NO 3 ) 3 ϩ KOH 0 Al(OH) 3 ϩ KNO 3
d. Hg 2 O 0 HgO ϩ Hg
8. Determine the oxidation number of bromine in each of the
following compounds. Explain your answers.
a. LiBr
b. BrF 3
c. Mg(BrO 3 ) 2
9. Which element is a stronger oxidizing agent—iodine or
chlorine? Explain.
10. Write a balanced equation for the high-temperature reaction of
iron(III) oxide and carbon monoxide gas to form molten iron
metal and carbon dioxide gas.
11. Balance the following redox equation by using the half-reaction
method. Explain the steps you followed. Give the final equation
as it is shown below but with the balancing coefficients.
HClO 3 (aq) 0 HClO 4 (aq) ϩ ClO 2 (g) ϩ H 2 O(l)