Q1. [4] § 3.1 PHYSICAL PROPERTIES § 3.2 CHEMICAL PROPERTIES OF METALS § 3.4 OCCURRENCE OF METALS
The metals produced by various reduction processes are not very pure. They contain impurities, which must be removed to obtain pure metals. The most widely used method for refining impure metals is electrolytic refining.
Read the source given and answer the questions that follow :
- (i) What is the cathode and anode made of in the refining of copper by this process ? [1]
- (ii) Name the solution used in the above process and write its formula. [1]
- (iii) How copper gets refined when electric current is passed in the electrolytic cell ? [2]
Previously asked in CBSE board exam
2024 31/1/1 Q37
Generated by claude-sonnet-4-6 · 2026-06-15 06:49 · grounding stimulus
Model Answer
(i) In the electrolytic refining of copper:
- Anode — impure copper
- Cathode — pure (thin strip of) copper
(ii) The solution used is acidified copper sulphate solution.
Formula: CuSO₄
(iii) When electric current is passed:
- The impure copper anode slowly dissolves into the solution, releasing Cu²⁺ ions.
- These Cu²⁺ ions migrate to the cathode and deposit as pure copper.
- The insoluble impurities (such as gold, silver) from the anode settle at the bottom as anode mud.
- Thus, pure copper gets collected at the cathode.
Source: Chapter 3 – Metals and Non-metals, Electrolytic Refining
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Explanation
- (i) is a direct recall fact — anode = impure metal, cathode = pure metal. Don't reverse them.
- (ii) Examiners expect both the name AND formula; writing only one loses the mark.
- (iii) For 2 marks, cover two key steps: anode dissolving + cathode deposition. Mentioning anode mud is a bonus point that shows thorough knowledge.
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