Chem 1721/1821
Name _________________________________
Quiz 8 (20 points)
May 2, 2013
.!"#$!
! = !! – (
)!"#$ !" !"! !
!
F = 96,485 C/mol e–
rate = kN
1.
2.
3.
!! =
.!"#$!
!
!"#$ !" !"! !
1 V = 1J/C
t1/2 = .693/k
Indicate whether each of the following statements is True or False for the Galvanic cell described by the following line
notation: Sn (s) | Sn2+ (aq) || MnO4— (aq), H+ (aq), Mn2+ (aq) | C (s).
a.
This cell runs spontaneously in the direction that consumes Mn2+ (aq).
_______________
b.
Sn (s) functions as an inert electrode.
_______________
c.
The direction of electron flow in this cell is from tin to graphite.
_______________
d.
For this reaction ΔG° will be negative because E° will be negative.
_______________
e.
In this cell, permanganate ion functions as the oxidizing agent.
_______________
Refer to the list of half-reactions given on the periodic table, and then consider a Galvanic cell based on the Cl2/Cl— redox
couple and the Fe3+/Fe2+ redox couple.
a.
Write the anode half-reaction for this cell.
____________________________________________________
b.
Write the balanced net cell reaction.
____________________________________________________
Refer to the list of half-reactions given on the periodic table, and then answer the following questions.
a.
4.
ΔG° = −nFE°
1 A = 1 C/s
ln(N/N0) = −kt
Identify the strongest reducing agent in this list.
_______________
—
b.
True or False? NO3 ions in acidic solution can cause the oxidation of gold.
_______________
c.
True or False? The oxidation of H2 by O2 in acidic solution is a spontaneous reaction.
_______________
Consider an electrochemical cell with this net reaction: 2 MnO4— (aq) + Pb (s)  Pb2+ (aq) + 2 MnO42— (aq); E° = 0.69 V
a.
Calculate ΔGº (in kJ) for this reaction.
ΔGº = __________________ kJ
b.
This cell operates with E = 0.57 V at 25°C when [Pb2+] = 0.333 M and [MnO42—] = 0.457 M. Calculate [MnO4—]
under these conditions.
[MnO4—] = __________________ M
5.
Refer to the list of half-reactions given on the periodic table, and then consider a Galvanic cell in which the following
reaction occurs: Cr + Zn2+  Cr2+ + Zn. Determine the value of the equilibrium constant, K, for this reaction at 25ºC.
K = __________________
6.
Calculate the current (in amps) required to plate 1.5 kg of cobalt from CoCl3 (aq) during an 8.0-hour shift.
current = ________________ A
7.
a.
Write the balanced equation that describes β-emission from phosphorus-32.
b.
α-emission of a radioactive nuclide produces lead-206. Which one of the following is the parent nuclide (the
reactant) in this nuclear transformation? Circle the one best answer below.
!"!
!"Hg
c.
!"#
!"Po
!"#
!"Pt
!"#
!"Rn
Which of the following types of nuclear decay results in no change in the atomic number? Circle the one best
answer below.
α emission
β emission
electron capture
8.
!"#
!"Rn
γ emission
β+ emission
all of these result in a change in atomic number
198
Au is a radioactive isotope. After 3.5 days, 40.5% of the radioactive nuclei in a gold-198 sample remain. Determine
the decay constant (k, in s—1) and the half-life (in s) for 198Au.
k = __________________ s—1
t1/2 = ___________________ s
Periodic Table of the Elements
IA
II A
III B
IV B
VB
VI B
VII B
VIII
IB
II B
III A
IV A
VA
VI A
VII A inert
gases
1
2
H
He
1.008
4.003
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
6.941 9.012
11
10.81 12.01 14.01 16.00 19.00 20.17
12
Na Mg
22.98 24.31
13
14
15
16
17
18
Al
Si
P
S
Cl
Ar
26.98 28.09 30.97 32.06 35.45 39.95
19
20
21
22
23
24
K
Ca
Sc
Ti
V
Cr
25
26
27
28
Mn Fe Co
Ni
29
30
31
32
33
Cu Zn Ga Ge As
34
35
36
Se
Br
Kr
39.10 40.08 44.96 47.90 50.94 52.00 54.94 55.85 58.93 58.71 63.55 65.37 69.72 72.59 74.92 78.96 79.90 83.80
37
38
39
40
Rb
Sr
Y
Zr
41
42
43
Nb Mo Tc
44
45
46
47
48
Ru Rh Pd Ag Cd
49
In
50
51
Sn Sb
52
53
54
Te
I
Xe
85.46 87.62 88.91 91.22 92.91 95.94 98.91 101.0 102.9 106.4 107.8 112.4 114.8 118.6 121.8 127.6 126.9 131.3
55
56
Cs
Ba
*
57
72
73
74
La
Hf
Ta
W
75
76
Re Os
77
78
Ir
Pt
79
80
Au Hg
81
82
83
84
85
86
Tl
Pb
Bi
Po
At
Rn
132.9 137.3 138.9 178.4 180.9 183.8 186.2 190.2 192.2 195.0 196.9 200.5 204.3 207.2 208.9 (210) (210) (222)
87
88
Fr
Ra
*
89
104
Ac Rf
(223) 226.0 (227) (261)
108
109
Db Sg
105
Bh Hs
Mt
(262)
(263)
(262)
60
61
58
59
Ce
Pr
106
107
(265) (266)
62
110
111
112
113
114
(269)
(272)
(277)
?
(289)
63
Nd Pm Sm Eu
140.1 140.9 144.2 (147) 150.4 151.9
90
91
92
Th
Pa
U
93
94
95
64
65
Gd
Tb
66
(242)
(243)
96
97
98
(247)
Cf
69
70
(247)
99
(251) (254)
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
Eº
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
100
101
102
Es Fm Md No
Abridged Table of Standard Reduction Potentials:
Mg2+ + 2 e—  Mg
Cr2+ + 2 e—  Cr
Ti3+ + e—  Ti2+
Zn2+ + 2 e—  Zn
PbSO4 + 2 e—  Pb2+ + SO42—
2 H + + 2 e—  H 2
Cu2+ + 2 e—  Cu
Cu+ + e—  Cu
Fe3+ + e—  Fe2+
NO3— + 4 H+ + 3 e—  NO + 2 H2O
O2 + 4 H+ + 4 e—  2 H2O
Cr2O72— + 14 H+ + 6 e—  2 Cr3+ + 7 H2O
Cl2 + 2 e—  2 Cl—
Au3+ + 3 e—  Au
MnO4— + 4 H+ + 3 e—  MnO2 + 2 H2O
Co3+ + e—  Co2+
68
Er Tm Yb
71
Lu
157.3 158.9 162.5 164.9 167.3 168.9 173.0 174.9
Np Pu Am Cm Bk
232.0 (231) 238.0 (237)
67
Dy Ho
–2.37 V
–0.91 V
–0.85 V
–0.76 V
–0.35V
0.000 V
0.34V
0.52 V
0.77 V
0.96 V
1.23 V
1.33 V
1.36 V
1.50 V
1.68 V
1.82 V
(253)
(256)
(254)
103
Lr
(257)