STANDARD Chemistry Electrolysis MCQ Question
The Gibbs energy for the decomposition of Al₂O₃ at 500°C is as follows : 2/3Al₂O₃ → 4/3Al + O₂ ; ΔG = +966 kJ/mol. The potential difference needed for electrolytic reduction of Al₂O₃ at 500°C is at least
5.0 V
4.5 V
3.0 V
2.5 V
Correct Answer
Detailed Explanation
The ionic reactions are: 2/3 × (2Al³⁺) + 4e⁻ → 4/3 Al and 2/3 × (3O²⁻) → O₂ + 4e⁻. The number of electrons transferred, n = 4. Using the equation G = -nFE, we find E = -966 × 10³ / 4 × 96500 = -2.5 V.
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