Alumina, Al₂O₃, is amphoteric. Among examples of its amphoteric character are the reactions that occur when Al₂O₃ is heated strongly or “fused” with acidic oxides and basic oxides.
(a) Write a balanced equation for the reaction of alumina with silica, an acidic oxide, to give aluminum metasilicate, Al₂(SiO₃)₃.
(b) Write a balanced equation for the reaction of alumina with the basic oxide CaO to give calcium aluminate, Ca(AlO₂)₂.