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Electrochemistry

Question

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Estimate the minimum potential difference needed to reduce Al₂O₃ at 500° C. The free energy change for the decomposition reaction.
$2 {Al}_{2} O_{3} \to \frac{4}{3} Al + O_{2} is ∆ G = + 960 kJ . (F = 96500 C {mol}^{- 1})$

Solution

Applying the formula:

∆ G ° = - nF ° E

960 \times 10^{3} J = - 4 \times E ° \times 96500 = \frac{- 960 \times 10^{3}}{4 \times 96500} = E °_{cell} E °_{cell} = \frac{- 96500}{3860} = - 2.487 V .

Since,

∆ G = + 960 kJ = + 960 \times 10^{3} J, E ° = ? F = 96500 C {mol}^{- 1} . \frac{4}{3} {Al}^{3 +} + 4 e^{-} \to \frac{4}{3} Al n = 4 .

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