Question

On the basis of electrochemical series, how would you predict feasibility of a redox reaction?

Answer 1

One of the major applications of the electrochemical series is to predict the feasibility of redox reactions.

For a redox reaction to be feasible, the species that gets oxidised (loses electrons) must have a lower standard reduction potential (E°), and the species that gets reduced (gains electrons) must have a higher standard reduction potential (E°).

Let us consider copper and silver:

\[\ce{E^{\circ}_{{Cu^{2+}/{Cu}}}}\] = +0.34 V

\[\ce{E^{\circ}_{{Ag^{+}/{Ag}}}}\] = +0.80 V

Reaction: \[\ce{Cu + 2Ag+ -> Cu^2+ + 2Ag}\]

Ag⁺ (higher E°) gets reduced to Ag.

Cu (lower E°) gets oxidised to Cu²⁺.

Since the more electropositive species (Ag⁺) is reduced and the less electropositive species (Cu) is oxidised, the reaction is feasible.

Reverse reaction: \[\ce{Cu^2+ + 2Ag -> Cu + 2Ag+}\]

This is not feasible, because it would involve oxidation of Ag (which has a higher E° than Cu), which goes against the electrochemical series.