When the equation for the following reaction in basic solution is balanced, what is the sum of the coefficients? MnO2 + HO2- ® MnO4–
A.
11
B.
31
C.
14
D.
9
E.
18
2.
Which of the following reactions is possible at the anode of a galvanic cell?
A.
Zn ® Zn2+ + 2e–
B.
Zn2+ + 2e– ® Zn
C.
Zn2+ + Cu ® Zn + Cu2+
D.
Zn + Cu2+ ® Zn2+ + Cu
E.
two of these
3.
Which of the following is true for the cell shown here? Zn(s) ú Zn2+(aq) úú Cr3+(aq) ú Cr(s)
A.
The electrons flow from the cathode to the anode.
B.
The electrons flow from the zinc to the chromium.
C.
The electrons flow from the chromium to the zinc.
D.
The chromium is oxidized.
E.
The zinc is reduced.
4.
Which of the following is the best reducing agent?
Cl2 + 2e– ® 2Cl–
E° = 1.36 V
Mg2+ + 2e– ® Mg
E° = –2.37 V
2H+ + 2e– ® H2
E° = 0.00 V
A.
Cl2
B.
H2
C.
Mg
D.
Mg2+
E.
Cl–
5.
Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment):
The standard reduction potentials are as follows:
Cr3+ + 3e– ® Cr(s)
E° = –0.73 V
Br2(aq) + 2e– ® 2Br–
E° = +1.09 V
Which of the following statements about this cell is false?
A.
This is a galvanic cell.
B.
Electrons flow from the Pt electrode to the Cr electrode.
C.
Reduction occurs at the Pt electrode.
D.
The cell is not at standard conditions.
E.
To complete the circuit, cations migrate into the left half-cell and anions migrate into the right half-cell from the salt bridge.
6.
A cell is set up with copper and lead electrodes in contact with CuSO4(aq) and Pb(NO3)2(aq), respectively, at 25°C. The standard reduction potentials are: Pb2+ + 2e– ® Pb E° = –0.13 V Cu2+ + 2e– ® Cu E° = +0.34 V If the Pb2+ and Cu2+ are each 1.0 M, the potential of the cell, in volts, is:
A.
0.46
B.
0.92
C.
0.22
D.
0.58
E.
none of these
7.
Consider an electrochemical cell with a cobalt electrode immersed in 1.0M Co2+ and a lead electrode immersed in 1.0M Pb2+.
Co2+ + 2e– ® Co
E° = –0.28 V
Pb2+ + 2e– ® Pb
E° = –0.13 V
Calculate E° for this cell
A.
–0.15 V
B.
0.15 V
C.
–0.41 V
D.
0.41 V
E.
none of these
8.
Consider an electrochemical cell with a cobalt electrode immersed in 1.0M Co2+ and a lead electrode immersed in 1.0M Pb2+.
Co2+ + 2e– ® Co
E° = –0.28 V
Pb2+ + 2e– ® Pb
E° = –0.13 V
Which of the electrodes is the cathode?
A.
The cobalt electrode.
B.
The lead electrode.
9.
Consider an electrochemical cell with a cobalt electrode immersed in 1.0M Co2+ and a lead electrode immersed in 1.0M Pb2+.
Co2+ + 2e– ® Co
E° = –0.28 V
Pb2+ + 2e– ® Pb
E° = –0.13 V
If [Co2+]0 is 0.0010 M and [Pb2+]0 is 0.10 M, calculate E.
A.
0.15 V
B.
0.091 V
C.
0.27 V
D.
0.21 V
E.
none of these
10.
Consider an electrochemical cell with a tin electrode immersed in 1.0 M Sn2+ and a nickel electrode immersed in 0.10 M Ni2+.
Sn2+ + 2e– ® Sn
E° = –0.14 V
Ni-2+ + 2e– ® Ni
E° = –0.23 V
Calculate E for this cell.
A.
0.09 V
B.
–0.37V
C.
0.12 V
D.
0.06 V
E.
none of these
11.
Consider an electrochemical cell with a tin electrode immersed in 1.0 M Sn2+ and a nickel electrode immersed in 0.10 M Ni2+.
Sn2+ + 2e– ® Sn
E° = –0.14 V
Ni-2+ + 2e– ® Ni
E° = –0.23 V
Calculate the concentration of Ni2+ if the cell is allowed to run to equilibrium at 25°C.
A.
1.1 M
B.
–0.10 M
C.
0.001 M
D.
1100 M
E.
none of these
12.
The galvanic cell described by Zn(s) ú Zn2+(aq) úú Cu2+(aq) ú Cu(s) has a standard cell potential of 1.101 volts. Given that Zn(s) ® Zn2+(aq) + 2e– has an oxidation potential of 0.762 volts, determine the reduction potential for Cu2+.
A.
–1.863 V
B.
1.863 V
C.
–0.339 V
D.
0.339 V
E.
none of these
13.
Choose the correct statement given the following information:
Fe3+(aq) + e– ® Fe2+(aq)
E° = 0.77 volt
Fe(CN)63– + e– ® Fe(CN)64-
E° = 0.36 volt
A.
Fe2+(aq) is more likely to be oxidized than Fe2+ complexed to CN–.
B.
Fe3+(aq) is more likely to be reduced than Fe3+ complexed to CN–.
C.
Both a and b are true.
D.
Complexation of Fe ions with CN– has no effect on their tendencies to become oxidized or reduced.
E.
None of these is true.
14.
For a reaction in a voltaic cell both DH° and DS° are positive. Which of the following statements is true?
A.
E°cell will increase with an increase in temperature.
B.
E°cell will decrease with an increase in temperature.
C.
E°cell will not change when the temperature increases.
D.
DG° > 0 for all temperatures.
E.
None of these statements is true.
15.
The standard free energies of formation of several aqueous species are:
kJ/mol
H+(aq)
0
H2O(l)
–237
CH3OH(aq)
–163
HCOOH(aq)
–351
e–
0
What is the standard reduction potential of methanoic acid in aqueous solution (i.e., for HCOOH + 4H+ + 4e– ® CH3OH + H2O)?
A.
+0.13 V
B.
+0.17 V
C.
+0.25 V
D.
–0.13 V
E.
–0.25 V
16.
A fuel cell designed to react grain alcohol with oxygen has the following net reaction: C2H5OH(l) + 3O2(g) ® 2CO2(g) + 3H2O(l) The maximum work one mole of alcohol can yield by this process is 1320 kJ. What is the theoretical maximum voltage this cell can achieve?
A.
0.760 V
B.
1.14 V
C.
2.01 V
D.
2.28 V
E.
13.7 V
17.
Determine DG° for a cell that utilizes the following reaction: Cl2(g) + 2Br– (aq) ® 2Cl– (aq) + Br2 (l) The standard reduction for the chlorine gas is 1.360 volts and the standard reduction for the bromine liquid is 1.077 volts.
A.
471 kJ
B.
236 kJ
C.
27.3 kJ
D.
54.6 kJ
E.
82.5 kJ
18.
Calculate E at 25°C for the cell shown above, given the following data:
Ag+ + e– ® Ag(s) E° = 0.80 V Ni2+ + 2e– ® Ni(s) E° = –0.23 V Ksp for AgCl = 1.6 ´ 10–10
A.
0.83 V
B.
0.54 V
C.
1.01 V
D.
2.98 V
E.
cannot be determined from the data given
19.
Refer to the following system: 3Ag(s) + NO3–(aq) + 4H+ (aq) ® 3Ag+(aq) + NO(g) + 2H2O(l)
Anode reaction:
Ag ® Ag+(aq) + le–
E° = –0.799 V
Cathode reaction:
NO3–(aq) + 4H+(aq) + 3e– ® NO(g) + 2H2O(l)
E° = 0.964 V
Determine the standard cell potential.
A.
1.763 V
B.
0.165 V
C.
1.422 V
D.
–1.433 V
E.
2.403 V
20.
Refer to the following system: 3Ag(s) + NO3–(aq) + 4H+ (aq) ® 3Ag+(aq) + NO(g) + 2H2O(l)
Anode reaction:
Ag ® Ag+(aq) + le–
E° = –0.799 V
Cathode reaction:
NO3–(aq) + 4H+(aq) + 3e– ® NO(g) + 2H2O(l)
E° = 0.964 V
Determine the equilibrium constant at 25°C.
A.
3.21 ´ 105
B.
6.41 ´ 102
C.
9.97 ´ 1012
D.
2.41 ´ 108
E.
4.43 ´ 1015
21.
Of Sn2+, Ag+, and/or Zn2+, which could be reduced by Cu?
A.
Sn2+
B.
Ag+
C.
Zn2+
D.
Two of them could be reduced by Cu.
E.
All of them could be reduced by Cu.
22.
You make a cell with a nickel electrode in a solution of nickel nitrate and a zinc electrode in a solution of zinc nitrate.
If you could increase the concentration of Zn2+, which of the following is true about the cell potential?
A.
It would increase.
B.
It would decrease.
C.
It would remain constant.
D.
Cannot be determined.
23.
A common car battery consists of six identical cells each of which carries out the reaction Pb + PbO2 + 2HSO4– + 2H+ ® 2PbSO4 + 2H2O
Suppose that in starting a car on a cold morning a current of 125 amperes is drawn for 15.0 seconds from a cell of the type described above. How many grams of Pb would be consumed? (The atomic weight of Pb is 207.19.)
A.
8.05
B.
2.01
C.
0.0180
D.
0.0360
E.
4.02
24.
An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic Cr2O72– solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs.
If oxidation of H2O occurs at the anode, how many moles of oxygen gas will evolve for every 1.00 ´ 102 grams of Cr(s) deposited?
A.
2.88
B.
0.48
C.
11.5
D.
7.7
E.
1.44
25.
An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic Cr2O72– solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs.
If the current is 10.0 amperes, how long will it take to deposit 100 ´ 102 grams of Cr(s) onto the bumper?
A.
10.3 h
B.
1.29 days
C.
309 min
D.
76.3 s
E.
2 mo, 25 days, 14 h, and 6 s
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