Cliffs AP Chemistry, 3rd Edition

5. Given the following information, which of the statements is true?

Cu2+(aq) + e–→Cu+(aq) E°red= 0.34 V

2 H+(aq) + 2 e–→H 2 (g) E°red= 0.00 V

Fe2+(aq) + 2 e–→Fe(s) E°red= -0.44 V

Ni(s) →Ni2+(aq) + 2 e– E°ox= 0.25 V

A. Cu2+(aq) is the strongest oxidizing agent.

B. Cu2+(aq) is the weakest oxidizing agent.

C. Ni(s) is the strongest oxidizing agent.

D. Fe(s) would be the weakest reducing agent.

E. H+(aq) would be the strongest oxidizing agent.

Answer: A

The more positive the E°redvalue, the greater the tendency for the substance to be reduced, and
conversely, the less likely it is to be oxidized. It would help in this example to reverse the last
equation so it can be easily compared to the other E°redvalues. The last equation becomes
Ni2+(aq) + 2e–(aq) →Ni(s); E°red= −0.25 V.

The equation with the largest E°redis Cu2+(aq) + e–→Cu+(aq); E°red= 0.34 V. Thus, Cu2+(aq) is
the strongest oxidizing agent of those listed because it has the greatest tendency to be reduced.
Conversely, Cu+(aq) would be the weakest reducing agent. Fe2+(aq) would be the weakest oxi-
dizing agent because it would be the most difficult species to reduce. Conversely, Fe(s) would
be the strongest reducing agent.

Part II: Specific Topics