Q1. [4] § 3.2 CHEMICAL PROPERTIES OF METALS § 3.4 OCCURRENCE OF METALS
An electrochemical process is used for refining metals by selectively dissolving and depositing them through electrolysis. Electrolytic refining is used for metals like Copper, Zinc, Tin, Nickel, Silver and Gold.
Read the following passage and answer the questions that follow :
- (a) Define anode mud. [1]
- (b) In electrolytic refining of copper, name the anode and the cathode. [1]
- (c) With the help of chemical equations, show the extraction of copper from its ore Cu₂S. [2]
Previously asked in CBSE board exam
2026 31/3/1 Q28
Generated by claude-sonnet-4-6 · 2026-06-15 06:46 · grounding stimulus
Model Answer
(a) During electrolytic refining, the impurities (like gold, silver, platinum) that settle below the anode at the bottom of the electrolytic solution are called anode mud.
(b)
- Anode: Impure copper (thick block)
- Cathode: Pure copper (thin strip)
(c) Extraction of copper from Cu₂S:
Step 1 – Roasting:
$$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$$
Step 2 – Reduction:
$$2Cu_2O + Cu_2S \rightarrow 6Cu + SO_2$$
Copper is obtained as a molten mass.
Source: Metals and Non-Metals, Electrolytic Refining & Extraction of Metals
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Explanation
- Anode mud is a standard definition question — mention that it settles below the anode and contains precious metal impurities.
- For (b), examiners expect both "impure copper = anode" and "pure copper = cathode" clearly stated.
- For (c), both steps (roasting + auto-reduction) with balanced equations are required for full 2 marks. Missing either equation costs a mark.
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