The Gibbs energy for the decomposition of Al₂O₃ at 500°C is as follows: 2/3Al₂O₃ → 4/3Al + O₂, ΔrG = +966 kJmol⁻¹. The potential difference needed for electrolytic reduction of Al₂O₃ at 500°C is at least:
5.0 V
2.5 V
4.5 V
3.0 V
Solution:
The correct option is C 2/3Al₂O₃ → 4/3Al + O₂ ΔG = -nFE E = -ΔG/nF = -(966 × 10³)/(4 × 96500) = 2.5V The potential difference needed for the reduction = 2.5V.