In it true that under certain conditions, Mg can reduce `Al_(2)O_(3)` and Al can reduce `MgO`? What are those conditions?

Explanation

Below the melting point of Al (1623 K), the curve of `Delta_(f)G^(@)" of "Al_(2)O_(3)` lies above that of `Delta_(f)G^(@)` and MgO. Therefore, at temperatures below 1623 K, Mg can reduce `Al_(2)O_(3)` to Al.
`Al_(2)O_(3)+3Mg overset(gt 1623K)rarr 3MgO+2Al, DeltaG^(@)=0ve`
Above 1623 K, the curve of `Delta_(f)G^(@)" of "Al_(2)O_(3)` lies below the corresponding curve of that of MgO.Therefore, above 1623 K, aluminium can reduce MgO to Mg.
`2Al+3MgO overset(lt 1623 K)rarr Al_(2)O_(3)+3Mg`