Electrochemistry
Practice Test
1.
Complete and balance the following redox equation. When properly balanced with whole—number coefficients, the coefficient of S is _________.
H
2
S + HNO
3
→ S + NO + H
2
O
a.
3
b.
1
c.
4
d.
2
2.
Compared to strong acids, weak acids produce __________ ions and conduct electricity __________ efficiently.
a.
fewer, less
b.
more, less
c.
more, more
d.
fewer, more
3.
Which of the following is the weakest reducing agent?
a.
Al
3+
b.
F
-
c.
F
2
d.
Al
4.
The molar solubility for BaCO
3
is 9.0 x 10
-5
M
at 25°C. What is the solubility product constant,
K
sp
, for BaCO
3
?
a.
4.0 x 10
-15
b.
5.3 x 10
-12
c.
8.1 x 10
-9
d.
1.2 x 10
-8
5.
In a voltaic cell, the salt bridge __________.
a.
is not necessary for the cell to work
b.
drives electrons from one half-cell to another
c.
acts as a mechanism to allow mechanical mixing of the solutions
d.
allows charge balance to be maintained in the cell
6.
A redox reaction that is not easily reversed is the source of electric energy in a(n) _______.
a.
primary battery
b.
secondary battery
c.
fuel cell
d.
electrolytic cell
7.
The Hall-Héroult process, which is used to make aluminum metal, electrolyzes a molten mixture of aluminum oxide and cryolite (Na
3
AlF
6
) to reduce aluminum cations to aluminum metal. Why is the cryolite used in this mixture?
a.
The cryolite raises the cell potential for the reduction of aluminum cations.
b.
The cryolite increases the conductivity of the mixture.
c.
The cryolite lowers the cell potential for the reduction of aluminum cations.
d.
The cryolite lowers the melting point of the mixture and thereby lowers the cost of manufacture by lowering the amount of heat energy needed to melt the mixture.
8.
For the reaction, 2SO
2
(g) + O
2
(g) → 2SO
3
(g) + heat, at equilibrium, what will be the effect on the net amount of SO
3
present if the temperature of the container is increased?
a.
This question cannot be answered without knowing the value of Keq.
b.
The concentration of SO
3
decreases.
c.
The concentration of SO
3
remains the same.
d.
The concentration of SO
3
increases.
9.
The pieces of metal that are placed on the outside of ships to help prevent corrosion are _________.
a.
sacrificial cathodes
b.
sacrificial anodes
c.
electrolyzed metals
d.
galvanized metals
10.
Determine the net change in oxidation number of chlorine in the following reaction:
ClO
4
-
(aq) + Br
-
(aq) → Cl
-
(aq) + Br
2
(g) (in acid solution)
a.
-8
b.
7
c.
-7
d.
8
11.
If NaCl is added to a 0.010M solution of AgNO
3
in water at 25°C, what will be [Cl
-
] when precipitation of AgCl begins? The Ksp for AgCl is 1.8 x 10
-10
.
a.
1.0 x 10
-10
M
b.
1.8 x 10
-12
M
c.
1.3 x 10
-6
M
d.
1.8 x 10
-8
M
12.
A 0.001
M
solution of HCl is ____________.
a.
a weak acid solution
b.
a dilute acid solution
c.
neutral
d.
a concentrated acid solution
13.
Neutralization is the chemical process in which ____________.
a.
sodium ions react with chloride ions to form sodium chloride
b.
sodium ions react with hydroxide ions to form sodium hydroxide
c.
hydrogen ions react with hydroxide ions to form water
d.
hydrogen ions react with chloride ions to form hydrogen chloride
14.
Balance the following equation. How many electrons must be transferred between the reducing agent and the oxidizing agent in this reaction?
H
2
S + HNO
3
→ S + NO + H
2
0
a.
2
b.
6
c.
4
d.
3
15.
In the following reaction, which chemical species is the oxidizing agent?
5H
2
O
2
+ 2MnO
4
-
+ 6H
+
→ 2Mn
2+
+ 8H
2
O + 5O
2
a.
Mn
2+
b.
H
2
O
2
c.
MnO
4
-
d.
H
+
16.
The highest possible oxidation number for carbon is ________.
a.
2
b.
4
c.
6
d.
+8
17.
Which of the following half-reactions represents oxidation?
a.
Fe
3+
+ 3e
-
→ Fe
b.
Fe → Fe
2+
+ 2e
-
c.
Cu
2+
+ 2e
-
→ Cu
d.
O
2
+ 4e
-
→ 2O
2-
18.
For the reaction, 2Cl
2
(g) + 2H
2
O(g) + heat → 4HCl(g) + O
2
(g), which of the following will shift the equilibrium to produce more HCl?
a.
decrease the volume of the reaction vessel
b.
lower the temperature of the reaction
c.
add more Cl
2
d.
add more O
2
19.
The electrolysis of an aqueous sodium chloride solution using inert electrodes produces gaseous chlorine at one electrode. At the other electrode, gaseous hydrogen is produced, and the solution around the electrode becomes basic. Which of the following equations is the correct equation for the cathode half-reaction in this electrolytic cell?
a.
2Cl
-
→ Cl
2
+ 2e
-
b.
2H
2
O + 2e
-
→ H
2
+ 2OH
-
c.
Cl
2
+ 2e
-
→ 2Cl
-
d.
H
2
+ 2OH
-
→ 2H
2
O + 2e
-
20.
Which of the following salts will produce a basic solution?
a.
KCN
b.
KBr
c.
NaCl
d.
Ca(NO
3
)
2
