Question

1.) A voltaic cell has a copper anode in 1 M CuSO₄ and a silver cathode in 1 M AgNO₃. What is Ecell for this cell?

A. +0.270 V
B. -1.137 V
C. +1.137 V
D. -0.463 V
E. +0.463 V

2.) Which of the following half-reactions is not correct?

A. Cu+ + e- → Cu
B. Mg → Mg2+ + 2e-
C. Fe3+ + 2e- → Fe+
D. Pb2+ + e- → Pb3+
E. Ag → Ag+ + e-

Answer 1

1. Reduction potential of Cu2+ = 0.34 V

Reduction potential of Ag+ = 0.800 V

So, Ag+ will oxidise Cu.

E^o_cell = 0.80-0.34 = 0.46 V

Ecell = E^o_cell -0.06/n log[Cu2+]/[Ag+]²

= 0.46 - 0.06/2 log[1]/[1]²

= 0.46 V

Answer is E.

2. In all the reactions, charges are balanced on both the sides of the reaction except one reaction.

Pb²⁺ + e- --------> Pb³⁺

The reaction should be:

Pb²⁺ --------> Pb³⁺ + e- ​

Now the charges are balanced on both sides of the reaction.

Answer is D.