Question

The Gibbs energy for the decomposition of `Al_(2)O_(3)` at `500^(@)C` is as follows:
`(2)/(3)Al_(2)O_(3) rarr (4)/(3)Al + O_(2), Delta_(r)G = +966kJ mol^(-1)`
The potential difference needed for electrolytic reeduction of `Al_(2)O_(3)` at `500^(@)C` is at least:
A. 4.5 V
B. 3.0 V
C. 2.5 V
D. 5.0 V

Answer 1

Correct Answer - C
`(2)/(3)Al_(2)O_(3)to(4)/(3)Al+O_(2)`
`triangle_(r)G=+966kJmol^(-1)=966xx10^(3)Jmol^(-1)`
`triangleG=-nFE_(cell)`
`966xx10^(3)=-4xx96500xxE_(cell)`
`E_(cell)=2.5V`