In the electrolytic refining of copper, which of the following acts as the anode ?

Question

Examoogle · Accepted Answer

The correct answer is Option D: Impure copper block. In the electrolytic refining of copper, an impure block of copper serves as the anode, while a thin strip of pure copper serves as the cathode. During electrolysis, the impure copper dissolves into the electrolyte, and pure copper is deposited onto the cathode.

Step-by-Step Solution & Concepts:
In the electrolytic refining of copper, an impure block of copper serves as the anode, while a thin strip of pure copper serves as the cathode. During electrolysis, the impure copper dissolves into the electrolyte, and pure copper is deposited onto the cathode.

Working Principle: When an electric current is passed through the acidified copper sulphate solution, the impure copper anode undergoes oxidation: $Cu(s) \rightarrow Cu^{2+}(aq) + 2e^{-}$. Simultaneously, the copper ions in the solution migrate to the pure copper cathode where they undergo reduction: $Cu^{2+}(aq) + 2e^{-} \rightarrow Cu(s)$, effectively purifying the copper.

Key Formulas: $Cu(s) \rightarrow Cu^{2+}(aq) + 2e^{-}$ — Oxidation half-reaction at the anode; $Cu^{2+}(aq) + 2e^{-} \rightarrow Cu(s)$ — Reduction half-reaction at the cathode

Key Points: Electrolyte used is acidified copper sulphate ($CuSO_{4} + H_{2}SO_{4}$); Pure copper is deposited at the cathode; Impurities like gold, silver, and platinum settle as 'anode mud' at the bottom of the tank; The process increases the purity of copper up to 99.99%

Advantages: Produces high-purity copper suitable for electrical applications; Allows recovery of precious metals like silver and gold

Disadvantages: Energy-intensive process requiring continuous electrical supply; Requires careful management of the electrolyte and anode mud

Applications: Production of copper wires for electrical circuits; Purification of metals in metallurgical industries

Additional Info: Anode mud contains noble metals that are insoluble in the electrolyte. Option B (Copper sulphate) acts as the electrolyte, not an electrode. Option C (Carbon electrode) is inert and typically used in electrolysis of water or molten salts, not copper refining

Answer: D is correct — The impure copper block acts as the anode, which gradually dissolves into the electrolyte during the refining process.

Exam Tip: Always remember that in all electrolytic cells, the anode is the positive terminal where oxidation occurs, while the cathode is the negative terminal where reduction occurs.

Examoogle · Answer

Option A: Pure copper plate

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Option B: Copper sulphate solution

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Option C: Carbon electrode

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