Reason — Electrolytic refining is a process by which metals containing impurities are purified electrolytically to give a pure metal. Option 2 shows the set-up used for electrolytic refining of copper:
- Anode – impure copper block (loses electrons and goes into solution).
Cu - 2e- ⟶ Cu2+ - Cathode – thin sheet of pure copper (gains mass as metal is deposited).
Cu2+ + 2e- ⟶ Cu - Electrolyte – acidified aqueous CuSO₄ solution.
As current passes, pure copper is transferred from the impure anode to the cathode, while insoluble impurities collect below the anode as "anode mud".