O-LevelChemistryElectrolysis5070/12 · May/June 2022 · Q171 Mark
Aluminium can be extracted by the electrolysis of aluminium oxide dissolved in molten cryolite. Which reactions take place during the electrolysis?
AAl⁺ + e⁻ → Al (reaction at the anode), O²⁻ + 2e⁻ → O (reaction at the cathode)
BAl³⁺ + 3e⁻ → Al (reaction at the anode), 2O²⁻ + 4e⁻ → O₂ (reaction at the cathode)
CO²⁻ – 2e⁻ → O (reaction at the anode), 3Al⁺ + 3e⁻ → 3Al (reaction at the cathode)
D2O²⁻ – 4e⁻ → O₂ (reaction at the anode), Al³⁺ + 3e⁻ → Al (reaction at the cathode)
✓ Correct answer
D: 2O²⁻ – 4e⁻ → O₂ (reaction at the anode), Al³⁺ + 3e⁻ → Al (reaction at the cathode)
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