Question

In an aqueous mixture of aluminum, lead, and iron salts, which of these will be reduced first upon application of an electric current?

(A) Al3+ + 3e− → Al (s) Eo = −1.66V
(B) Pb2+ + 2e− → Pb (s) Eo = −0.13V
(C) Fe2+ + 2e− → Fe (s) Eo = −0.45V
(D) Fe3+ + 3e− → Fe (s) Eo = −0.036V

Answer 1

D) Fe3+ + 3e− → Fe (s) Eo = −0.036V

Step-by-step explanation:

In electrolysis we have to add electrical energy for redox reactions non-spontaneous because ΔºG is positive.

These 4 reduction reactions are all non-spontaneous because their reduction potentials are negative (ΔGº = - nFεº , ΔGº will be positive). So the ion most easily reduced is the least negative, in this case Fe3+ + 3e− → Fe (s) Eo = −0.036V.