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The Gibbs energy for the decomposition of Al2O3 at 500°C is as follows : 2/3 Al2O3 → 4/3 Al + O2, ΔrG = +966 kJ mol^-1 The potential difference needed for electrolytic reduction of Al2O3 at 500°C is at least
- 4.5 V
- 3.0 V
- 2.5 V
- 5.0 V
Correct answer: 2.5 V
Solution
The Gibbs energy change indicates the minimum energy required to drive the reaction, and the relationship between Gibbs energy and cell potential (E) is given by the equation ΔrG = -nFE. By rearranging this equation, we can calculate the minimum potential difference needed for the electrolytic reduction, which results in a value of 2.5 V.
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