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Question

Chemistry Question on Thermodynamics

The Gibbs' energy for the decomposition of Al2O3 {Al2O3 } at 500C500^{\circ} C is as follows: 23Al2O3>43Al+O2;ΔrG=+960kJmol1 { \frac{2}{3} Al_2 O_3 -> \frac{4}{3} Al + O_2 ; \Delta_r G = + 960 \, kJ \, mol^{-1} } The potential difference needed for the electrolytic reduction of aluminium oxide (Al2O3) {(Al2O3)} at 500C500^{\circ} C is at least

A

3.0V3.0\, V

B

2.5V2.5\, V

C

5.0V5.0\, V

D

4.5V4.5\, V

Answer

2.5V2.5\, V

Explanation

Solution

ΔG=nFE\Delta G^{\circ} = - nFE^{\circ} 960×1000=4×96500×E960 \times 1000 = - 4 \times 96500 \times E^{\circ} E=2.48VE^{\circ} = - 2.48 V So difference = 2.5V2.5\, V