General Chemistry Ii Jasperse - Electrochemistry Extra Practice Problems With Answers Page 6
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136
2+
28. Given the electrochemical reaction shown, if the standard reduction potential of Zn
! Zn is –0.76 V, what is the
2+
! Mg?
standard reduction potential of Mg
2+
2+
Mg / Mg
(aq) // Zn
(aq) / Zn
E˚ = +1.61 V
a. –0.85 V
T
1. Solve for magnesium Eº(ox)
b. +0.85 V
2. To get Eº(red), reverse the +/- sign
c. +2.37 V
d. –2.37 V
e. none of the above
2+
! Cu is +0.34 V, what is the
29. Given the electrochemical reaction shown, if the standard reduction potential of Cu
2+
standard reduction potential of Sn
! Sn?
2+
2+
Sn / Sn
(aq) // Cu
(aq) / Cu
E˚ = +0.48 V
a. –0.14 V
b. +0.14 V
c. +0.37 V
d. –0.37 V
e. none of the above
30. Identify the strongest reducing agent based on the following half-reactions. The standard reduction potentials are listed.
+
–
2+
+1.22 V
MnO
(s) + 4H
(aq) + 2e
→ Mn
(aq) + 2H
O(l)
2
2
–
2–
+0.61 V
Hg
SO
(s) + 2e
→ 2Hg(l) + SO
(aq)
2
4
4
–
–
–0.95 V
SnO
(s) + 2H
O() + 4e
→ Sn(s) + 4OH
(aq)
2
2
–
–
–1.48 V
Cr(OH)
(s) + 3e
→ Cr(s) + 3OH
(aq)
3
Oxidizing agents
Reducing agents
T
a.
Cr
d.
Sn
b.
MnO
e.
Hg
2
c.
Hg
SO
2
4
31. Identify the strongest oxidizing agent from the following half-reactions. The standard reduction potentials are listed.
+
–
2+
+1.22 V
MnO
(s) + 4H
(aq) + 2e
→ Mn
(aq) + 2H
O(l)
2
2
–
2–
+0.61 V
Hg
SO
(s) + 2e
→ 2Hg(l) + SO
(aq)
2
4
4
–
–
–0.95 V
SnO
(s) + 2H
O() + 4e
→ Sn(s) + 4OH
(aq)
2
2
–
–
–1.48 V
Cr(OH)
(s) + 3e
→ Cr(s) + 3OH
(aq)
3
Oxidizing agents
Reducing agents
a.
Cr
d.
Sn
b.
MnO
e.
Hg
2
c.
Hg
SO
2
4
32. In one episode of the TV sitcom, Gilligan’s Island, the “professor” constructed voltaic cells to use as substitutes for
their radio’s dead batteries. Which scraps of metal from their damaged boat, the Minnow, could best be used to
create a 1.5 V voltaic cell? (Assume that coconuts make great beakers and that seawater is a terrific electrolyte!)
Metal/Metal ion
E
lead/lead(II) (fishing weights)
–0.126
T
iron/iron(II) (the anchor)
–0.44
silver/silver(I) (Mrs. Howell’s brooch)
–0.799
aluminum/aluminum(III) (the boat’s flagpole)
–1.677
a.
silver anode and lead cathode
d.
aluminum anode and silver cathode
b.
aluminum anode and lead cathode
e.
lead cathode and silver anode
c.
iron anode and aluminum cathode
To get the correct approximate voltage, choose an oxidation and
redution pair that sum appropriately.
Cathode: reduction element (lead)
Anode: oxidation (aluminum)
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