3. Consider the following half-reactions and select the strongest oxidizing agent present:
Sr
2+
(
aq
) + 2e
-
→
Sr(
s
)
E
° = -2.89 V
Cr
2+
(
aq
) + 2e
-
→
Cr(
s
)
E
° = -0.913 V
Co
2+
(
aq
) + 2e
-
→
Co(
s
)
E
° = -0.28 V
a.
Cr
2+
(
aq
)
b.
Sr
2+
(
aq
)
c.
Co
2+
(
aq
)
d.
Sr(
s
)
e.
Co(
s
)
4. In an electrolytic cell, how many grams of Cu could be plated out of a CuSO
4
solution
at a current of 5.00 A for 2.00 min? (
F
= 96500 C/mol)
a.
318 g
b.
0.395 g
c.
0.329 x 10
-3
g
d.
0.198 g
e.
5.31 g
5. A voltaic cell is based on the following two half-reactions:
Ni
+2
(
aq
) + 2e
-
→
Ni(
s
)
E
° = -0.25 V
Cr
+3
(
aq
) + 3e
-
→
Cr(
s
)
E
° = -0.74 V
Sketch the cell and then select the correct statement about it.
a. Cr serves as the cathode.
b. The direction of electron flow through the external wire is from the Ni to the Cr
electrode.
c. Anions in solution will migrate
toward
the Ni
+2
/Ni electrode.
d. The net cell reaction is 3Ni
+2
(
aq
) + 2Cr(
s
)
→
3Ni(
s
) + 2Cr
+3
(
aq
)
e.
E
°
cell
= 0.99 V
6. Consider the following two electrode reactions and their standard electrode potentials:
Al
+3
(
aq
) + 3e
-
→
Al (
s
)
E
° = -1.66 V
Cd
+2
(
aq
) + 2e
-
→
Cd(
s
)
E
° = -0.40 V
Write the cell reaction for a voltaic cell based on these two electrodes, and calculate the
standard cell potential,
E
°
cell
.
a. 2Al
+3
(
aq
) + 3Cd
+2
(
aq
)
→
2Al(
s
) + 3Cd(
s
)
E
°
cell
= 2.10 V
b. 2Al(
s
) + 3Cd
+2
(
aq
)
→
2Al
+3
(
aq
) + 3Cd(
s
)
E
°
cell
= 1.26 V
c. 2Al(
s
) + 3Cd
+2
(
aq
)
→
2Al
+3
(
aq
) + 3Cd(
s
)
E
°
cell
= 3.78V
d. 2Al
+3
(
aq
) + 3Cd(
s
)
→
2Al(
s
) + 3Cd
+2
(
aq
)
E
°
cell
= 1.26 V
e. 2Al
+3
(
aq
) + 3Cd(
s
)
→
2Al(
s
) + 3Cd
+2
(
aq
)
E
°
cell
= 2.10 V
