Aluminium is extracted electrolysis from

Analyze the question: The question asks which material is the ore from which aluminium is extracted by electrolysis.

Explain the concept: Aluminium is a very reactive metal, so it cannot be extracted by heating with carbon. It is extracted by electrolysis using the Hall-Héroult process:

1. Purification of the ore: The ore is first purified (the Bayer process) to give pure aluminium oxide, Al₂O₃ (alumina).
2. Electrolysis: The alumina is dissolved in molten cryolite (Na₃AlF₆). Cryolite lowers the melting point from about 2000°C to about 900°C, which saves energy, and it improves conductivity.
3. Electrode reactions: • Cathode (carbon lining): Al³⁺ + 3e⁻ → Al • Anode (graphite): 2O²⁻ → O₂ + 4e⁻

Check each option:

• A. Bauxite: This is the main ore of aluminium (hydrated aluminium oxide, Al₂O₃·2H₂O). It is the source of the alumina that is electrolysed. ✔
• B. Cryolite: This is not the source of the aluminium. It is only the solvent or electrolyte additive that lowers the melting point.
• C. Duralumin: This is an alloy of aluminium with copper, magnesium and manganese. It is made from aluminium, not used to extract it.
• D. Kaolin: This is aluminium silicate clay (china clay). It contains aluminium, but it is not used commercially for extraction.

Answer: The aluminium is extracted from bauxite, which is option A.

Exam tip: Remember "Bauxite is the Boss ore, Cryolite is the Co-worker." Bauxite supplies the aluminium, and cryolite only helps by lowering the melting point. WASSCE often tests this difference.