The Gibbs energy for the decomposition of `Al_(2)O_(3)` at `500^(@)C` is as follow :
`(2)/(3)Al_(2)O_(3) rarr (4)/(3)Al+O_(2), Delta_(r)G= +960 kJ mol^(-1)`
The potential difference needed for the electrolytic reduction of aluminium oxide `(Al_(2)O_(3))` at `500^(@)C` is