Which method is used for the purification of copper from its ore?

Analyze the question: The question asks which method is used to purify copper. Note the word "purification": this is the refining stage, not the extraction stage.

Explain the concept: Copper extraction and purification happen in stages:

1. Extraction: The ore (e.g. copper pyrites, CuFeS₂) is concentrated by froth flotation, then roasted and smelted. This gives "blister copper", which is about 98-99% pure.
2. Purification (refining): The impure copper is purified by electrolysis.

Solution (how electrolytic refining works):

• Anode: a block of impure copper
• Cathode: a thin strip of pure copper
• Electrolyte: copper(II) sulphate solution acidified with dilute sulphuric acid

Reactions:

• At the anode: Cu → Cu²⁺ + 2e⁻ (the impure copper dissolves)
• At the cathode: Cu²⁺ + 2e⁻ → Cu (pure copper deposits)

Impurities either fall to the bottom as "anode sludge" (such as silver, gold and platinum) or stay in solution (such as iron and zinc).

Checking the options:

• A. Distillation: separates liquids by boiling point. It does not apply here.
• B. Electrochemical: this is a broad term for processes involving electricity and chemical change. It is not the specific named method, and "electrolysis" is the standard answer.
• C. Electrolysis: the standard method for refining copper. ✔
• D. Neutralization: an acid-base reaction, not relevant.
• E. Reduction: it is used to extract metals from their compounds (for example, in smelting), not to purify the metal.

Answer: C. Electrolysis

Exam tip: Remember "Extract by reduction, refine by electrolysis." When a question says purification of copper, think of an impure copper anode and a pure copper cathode in CuSO₄ solution.