CSU Dominguez Hills
Chemistry 102 –Chemistry for the Citizens
Instructor: Dr. Kenneth R. Rodriguez, SP08
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Answer Key
Homework #6
You must show your entire work on a separate sheet(s) of paper to get full credit.
Chapter 10
1. Identify each of the following as an oxidation or a reduction reaction.
a. Zn2+ + 2e–  Zn b. Cu  Cu2+ + 2e– c. Fe  Fe3+ + 3e– d. I2 + 2e–  2I–
reduction
oxidization
oxidation
reduction
2. Why can Earth’s atmosphere be described as an oxidizing atmosphere?
The Earth’s atmosphere is an oxidizing atmosphere because the oxygen in the atmosphere
is reduced when it reacts with other substances to gain electrons and form O-2 ions. The
materials reacting with oxygen (iron for ex) are oxidized because they lose electrons to
the O atoms.
3. Indicate whether following reactions is a strong, weak, or nonelectrolyte represented
in the following equations:
a.
b.
c.
d.
K2SO4(s) (in H2O)  2K+(aq) + SO42-(aq)
NH4OH(aq) (in H2O)  NH4+ (aq) + OH- (aq)
C6H12O6(s) (in H2O)  C6H12O6(aq)
MgCl2(s) (in H2O)  Mg2+(aq) + 2Cl-(aq)
Strong electrolyte
Weak electrolyte
Nonelectrolyte
Strong electrolyte
4. Would you expect a piece of iron to rust on the surface of the moon? Explain.
No, I would not, because there is essentially no atmosphere on the moon so oxygen
would be available to react.
5. Besides electricity, what do the fuel cells used on the space shuttle produce?
The fuel cells use H2(g) and O2(g) to produce electrical energy and H2O. This provides
fresh drinking water.
6. Oxygen in the air reacting with substances in food can cause spoilage. Why are
antioxidants added to food?
Antioxidants react with the oxygen in air that touches the food so this oxygen cannot
react with the substances in the food to cause spoiling.
7. In addition to iron, what reactants are needed for the formation of rust?
Water, and oxygen, as well as iron, are required to produce rust
8. Tell which substance is reduced and which is oxidized in the following equations by
showing two separate reactions.
a. 2Al(s) + 3Cl2(g)  2AlCl3(s)
oxidized: Al
reduced: Cl2
b. S(s) + O2(g)  SO2(g)
oxidized: S
reduced: O2
c. CuO(s) + H2(g)  Cu(s) + H2O(g)
oxidized: H2
reduced: CuO
d. C2H4(g) + H2(g)  C2H6(g)
oxidized: H2
reduced: C2H4
9. The main source of magnesium is seawater, which contain Mg2+ ions. Is this
magnesium in an oxidation or reduced form?
Magnesium is oxidized in the Mg2+ ion because Mg metal has a zero charge. The
element loses two electrons when it forms the Mg2+ ion.
10. There are how many equivalents in the following ions:
a. 1 mole of Cu2+ b. 1 mole of Brc. 2 mole of Na+
2
1
2*(1)
d. 1 mole of N33