Predict conditions under which Al might be expected to reduce MgO.

Explanation

The equations for the formation of two oxides are
`(4)/(3)Al+O_(2) to (2)/(3) Al_(2)O_(3)`
`2Mg+O_(2) to 2MgO`
If we observe the plots for the formation of the two oxides on the Ellingham diagram, we find the two curves intersect each other at certain point. The corresponding value of `DeltaG^(@)` becomes zero-for the reduction of MgO by aluminium metal.
`2MgO +(4)/(3) Al to 2Mg +(2)/(3)Al_(2)O_(3)`
This means that the reduction of MgO by Al metal cannot occur below this temperature (1665 K), instead, Mg can reduce `Al_(2)O_(3)` to Al below 1665 K. Al can reduce MgO to Mg above 1665 K because `DeltaG^(@)` for `Al_(2)O_(3)` is less as compared to that of MgO.
`3MgO (s) + 2Al(s) underset(T gt 1665K) to Al_(2)O_(3)(s) +3Mg(s)`