The under certain conditions magnesium can be reduce `SiO_(2)` and silicon can reduce MgO. What are those conditions?

Explanation

Below 1973 K , the ` Delta _f G ^(@) ` curve for the formation of ` SiO _ 2 ` lies above the ` Delta _ f G ^(@) ` curve for the formation of MgO, therefore, at temperatures below 1973 K , Mg can reduce ` SiO _ 2 ` to metallic silicon
` " " SiO_2 + 2 Mg overset (lt 1973K)to 2 MgO + Si , Delta _r G ^(@) = - ve `
Above 1973K, the ` Delta _ f G^(@) ` curve for the formation of ` SiO_2 ` lies below the corresponding curve for the formastion of MgO. Therefore, above 1973 K, silicon can reduce MgO to Mg.
` " " Si + 2 MgO overset ( gt 1973K) to SiO _2 + 2 Mg `