The final step of the purification of copper involves electrorefining in which copper is separated from nickel and iron by being reduced at the cathode of a cell. Why are nickel and iron not reduced?
A)Their reduction potentials are more positive than copper's.
B)Their reduction potentials are more negative than copper's.
C)They cannot be deposited on a copper electrode.
D)Their reduction potentials are more negative than water's.
E)Their reduction requires large overvoltages.

Question

Quizplus · Accepted Answer

The reason why nickel and iron are not reduced in electrorefining is because their reduction potentials are more negative than copper's. As a result, when a potential is applied to the cell, copper ions are preferentially reduced at the cathode over nickel and iron ions.

The Final Step of the Purification of Copper Involves Electrorefining