Chemistry (Chang), 10th Edition

Chapter 19: Electrochemistry

Self Assessment B

1
When the following redox reaction is balanced, the coefficient for Cl2 will be _____, and ____ is the reducing agent. KMnO4(aq) + KCl(aq) + H2SO4(aq) ----> MnSO4(aq) + K2SO4(aq) + H2O(aq) + Cl2(g).
A)1; Mn2+
B)3; Cl-
C)3; MnO4-
D)5; Cl-
E)1; MnO4-
2
When the skeleton equation Zn + As2O3 ----> AsH3 + Zn2+, a reaction that is carried out in acid solution, is balanced, the coefficient for AsH3 will be ______.
A)1
B)2
C)3
D)5
E)8
3
Consider a voltaic cell constructed from a Ag(s) anode in 1.0 M AgNO3 and a Ni(s) cathode in 1.0 M Ni(NO3)2, linked by an external circuit and by a KCl salt bridge. The balanced overall (net) chemical equation for the cell reaction is
A)2 Ag(s) + Ni2+(aq) ----> 2 Ag+(aq) + Ni(s)
B)Ag(s) + Ni(s) ----> Ag+(aq) + Ni2+(aq)
C)Ag+(aq) + Ni(s) ----> Ag(s) + Ni2+(aq)
D)2 Ag+(aq) + Ni(s) ----> Ni2+(aq) + 2 Ag(s)
4
Consider a voltaic cell constructed from a Fe electrode in 1.0 M FeCl2 and a Ni electrode in 1.0 M Ni(NO3)2, linked by an external circuit and a KCl salt bridge. Based on the reduction potentials shown, which of the following statements is correct?

Fe2+ + 2 e- ----> Fe, Eo = -0.44 V;

Ni2+ + 2 e- ----> Ni(s), Eo = -0.25 V
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.
5
Given the following standard reduction potentials in acid solution, the species most likely to be reduced is:

Al3+ + 3 e- ----> Al(s) Eo = -1.66 V;

AgBr(s) + e- ----> Ag(s) + Br- Eo = 0.07 V;

Sn4+ + 2 e- ----> Sn2+ Eo = 0.14 V;

Fe3+ + e- ----> Fe2+ Eo = 0.77 V
A)Fe3+
B)Fe2+
C)Br-
D)Al3+
E)Al
6
Given the following standard reduction potentials in acid solution, which species is the strongest oxidizing agent?

Al3+ + 3 e- ----> Al Eo = -1.66 V;

Sn4+ + 2 e- ----> Sn2+ Eo = 0.14 V;

I2 + 2 e- ----> 2 I- Eo = 0.53 V
A)Al3+
B)Al
C)I-
D)I2
E)Sn4+
7
Calculate the free energy change per mole of Cu2+ formed in the following reaction at 25 oC.

Cu + 2 Ag+ ----> 2 Ag + Cu2+.

Cu2+ + 2 e- ----> Cu Eo = 0.34 V;

Ag+ + e- ----> Ag, Eo = 0.80 V.
A)0.46 kJ
B)89 kJ
C)44.5 kJ
D)-89 kJ
E)-0.46 kJ
8
What is Keq for the reaction Mg(s) + Pb2+ ----> Mg2+ + Pb at a temperature of 25oC?

Pb2+ + 2 e- ----> Pb, Eo = -0.13 V;

Mg2+ + 2 e- ----> Mg, Eo = -2.37 V.
A)6 x 1075
B)3 x 1084
C)2 x 10-75
D)None of the above.
9
What would you observe if you set up the following electrochemical cell: Ag|AgNO3(0.001 M)||AgNO3(1 M)|Ag?
A)Electrons will flow from left to right, causing a decrease in the AgNO3 concentration in the left cell, and an increase in the AgNO3 concentration in the right cell.
B)Electrons will flow from right to left, causing an increase in the AgNO3 concentration in the left cell, and a decrease in the AgNO3 concentration in the right cell.
C)Electrons will flow from left to right, causing an increase in the AgNO3 concentration in the left cell, and a decrease in AgNO3 concentration in the right cell.
D)Electrons will flow from right to left, causing a decrease in the AgNO3 concentration in the left cell, and an increase in the AgNO3 concentration in the right cell.
E)There will be no electron flow because the reduction potential at both electrodes is the same.
10
How many grams of the product formed at the cathode in the electrolysis of an aqueous solution of cupric chloride will be produced by a current of 1.0 A operating for 4.0 hrs?
A)2.3 g
B)4.7 g
C)6.9 g
D)8.0 g
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