The Gibbs energy for the decomposition of `Al_(2)O_(3)` at `500^(@)C` is as follows
`(2)/(3)A1_(2)O_(3)to (4)/(3) Al+O_(2), Delta_(r) G = + 966KJmol^(-1)`
The potential difference needed for electrolytic reduction of `Al_(2)O_(3)` at `500^(@)` is at least :

Options

A. 4.5 V
B. 3.0 V
C. 2.5 V
D. 5.0 V

Answer

C

Explanation

`underset(+6)(Al_(2)O_(3))tounderset(0)(2Al)+3/2O_(2),DeltaG=3/2xx966kJmol^(-1)`, n = 6. Then apply `DeltaG=-nFE`