In electrolytic refining of copper, the electrolyte is a solution of
- (a)acidified copper chloride.
- (b)acidified copper sulphate.
- (c)potassium chloride.
- (d)sodium sulphate.
Correct — B, acidified copper sulphate. In the electrolytic refining of copper the electrolyte is a solution of copper sulphate (CuSO₄) acidified with a little dilute sulphuric acid. Impure copper forms the anode and a thin strip of pure copper the cathode; when current flows, copper dissolves from the anode as Cu²⁺ and deposits as pure copper on the cathode. The electrolyte must carry the metal's own ions (Cu²⁺), which rules out potassium chloride and sodium sulphate, and the sulphate solution — not the chloride — is the one used in practice.
- (a)acidified copper chloride. — It does contain Cu²⁺ ions, but the standard industrial electrolyte for copper refining is acidified copper sulphate, not the chloride.
- (c)potassium chloride. — Potassium chloride contains no copper ions, so it cannot supply or deposit copper at the cathode — it is unusable for refining copper.
- (d)sodium sulphate. — Sodium sulphate has no Cu²⁺ ions; the electrolyte in electro-refining must contain ions of the metal being refined.
Electrolytic refining purifies an impure metal by making it the anode and a pure sample the cathode in a solution of a soluble salt of that metal. For copper the electrolyte is acidified copper sulphate; copper dissolves at the anode and plates out pure at the cathode, while impurities gather below as 'anode mud'.
The rule that 'the electrolyte carries ions of the metal being refined' at once eliminates the sodium and potassium salts. Between the two copper salts, the sulphate solution is the one used industrially.
- Copper is refined electrolytically using acidified copper sulphate solution as the electrolyte.
- The impure copper is the anode and pure copper is the cathode.
- Copper dissolves at the anode (Cu → Cu²⁺ + 2e⁻) and deposits at the cathode.
- Valuable impurities such as gold, silver and platinum settle below the anode as 'anode mud'.
- Choosing an electrolyte with no copper ions, such as KCl or Na₂SO₄.
- Picking copper chloride when the sulphate is the standard electrolyte.
Asked as 'which electrolyte for refining copper' — use the rule that the electrolyte carries ions of the metal being refined, then pick the sulphate.
No directly related past PYQ was found.
- practice — not a real PYQ
In the electrolytic refining of copper, the impure copper is used as the
- (a)cathode
- (b)anode
- (c)electrolyte
- (d)salt bridge
Answer(b) anode — it dissolves, and pure copper deposits on the cathode.
- practice — not a real PYQ
The valuable impurities left below the anode during the electro-refining of copper are called
- (a)slag
- (b)gangue
- (c)anode mud
- (d)flux
Answer(c) anode mud — it contains metals such as gold and silver.