7. Use the following standard electrode potentials to predict the species formed at the
electrodes in the electrolysis of aqueous CuSO
4
.
O
2
(
g
) + 4H
+
(
aq
) + 4e
-
→
2H
2
O(
l
)
E
° = +1.23 V
Cu
2+
(
aq
) + 2e
-
→
Cu(
s
)
E
° = +0.34 V
SO
4
2-
(
aq
) + 4H
+
(
aq
) + 2e
-
→
H
2
SO
3
(
aq
) + H
2
O(
l
)
E
° = 0.20 V
2H
+
(
aq
) + 2e
-
→
H
2
(
g
)
E
° = 0.00 V
a. H
2
, O
2
, H
+
b. Cu, O
2
, H
+
c. Cu,
H
2
d. H
2
, H
2
SO
3
, H
2
O
e. H
2
SO
3
, H
2
O, O
2
, H
+
8. A constant current was passed through a solution of KAuCl
4
between gold electrodes.
Over a period of 20.00 min, the cathode increased in mass by 2.664 g. What was the
current in amperes?
(
F
= 96500 C/mol)
Cathode half-reaction: AuCl
4
-
(
aq
) + 3e
-
→
Au(
s
) + 4Cl
-
(
aq
)
a. 1.08 A
b. 3.26 A
c. 2.17 A
d. 6.52 A
e. 3.48 A
9. A voltaic cell is constructed from the following half-cells, linked by a KCl salt bridge:
(a) an Fe electrode in 1.0
M
FeCl
2
solution
(b) a Ni electrode in 1.0
M
Ni(NO
3
)
2
solution
Use the table of standard electrode potentials in your textbook to decide which one of the
following statements is correct.
a.
The Ni electrode is the anode.
b.
Electrons flow from the iron electrode to the nickel electrode.
c.
The iron electrode is positively charged.
d.
The iron electrode will gain mass when current flows.
e.
The salt bridge conducts electrons through solution.
10. Which one of the following reactions must be carried out in an electrolytic cell, rather
than a voltaic cell?
a.
Zn + Cd
2+
→
Cd + Zn
2+
b.
Al + 3/2Br
2
→
Al
3+
+ 3Br
-
c.
2Al
3+
+ 3Fe
→
2Al + 3Fe
2+
d.
H
2
+ I
2
→
2H
+
+ 2I
-
e.
2H
2
+ O
2
→
2H
2
O