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:

Options

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

Answer

D

Explanation

`DeltaG =- nFE :. E = (-DeltaG)/(nF)`
`E = (-966 xx 103)/(4 xx 96500) =- 0.25`
`:.` The potential difference needed for the reduction `= 2.5V`