Suggest a condition under which magnesium could reduce alumina.

Explanation

The two equations are :
a) `(4)/(3)Al+O_(2)rarr(2)/(3)Al_(2)O_(3)" b) "2Mg+O_(2)rarr2MgO`
At the point of intersection of the `Al_(2)O_(3)` and MgO curves (marked ''A'' in Ellingham diagram), the `DeltaG^(Theta)` becomes ZERO for the reaction :
`(2)/(3)Al_(2)O_(3)+2Mg rarr 2MgO +(4)/(3)Al`
Below that point magnesium can reduce alumina.