The Equations for the formation of two oxides are
`(4)/(3)Al_((s))+O_(2_((g)))rarr(2)/(3)Al_(2)O_(3), 2Mg_((s))+O_(2_((g)))rarr2MgO_((s))`
from the Ellingham diagram the two curves of these oxides formation intersect each otherat a certain point .The corresponding value of `DeltaG^(@)` becomes Zero for the reducction of MgO by aluminium metal,
`2MgO_((s))+(4)/(3)Al_((s))hArr2Mg_((s))+(2)/(3)Al_(2)O_(3_((S)))`
`rarr` From the above information the reduction of MgO by Al metal connot occur below this temperature (1665 K) instead , Mg can reduce `Al_(2)O_(3)` to Al below 1665 K.
`rarr` Al-Metal can reduce MgO to Mg above 1665K becouse `DeltaG^(@)` for `Al_(2)O_(3)` is less compared to that of MgO.
`3MgO_((s))+2Al_((s))overset(Tgt1665K)rarrAl_(2)O_(3(s))+2Mg_((s))`
