Basic and Amphoteric Oxides of Metals

Metal oxides are crystalline solids that contain a metal cation and an oxide anion. They typically react with water to form bases or with acids to form salts. MO + H₂O → M(OH)₂ (where M = group 2 metal) Thus, these compounds are often called basic oxides.

Some metallic oxides get dissolved in water and form alkalis. Their aqueous solution turns red litmus blue.

Na₂O(s)+H₂O(l)→2NaOH(aq)
K₂O(s)+H₂O(l)→2KOH(aq)

Amphoteric Oxides of Metals

Amphoteric oxides are metal oxides which react with both acids as well as bases to form salt and water.
For example – Al₂O₃, ZnO, PbO, SnO
Al₂O₃(s)+6HCl(aq)→2AlCl₃(aq)+3H₂O(l)
Al₂O₃(s)+2NaOH(aq)→2NaAlO₂(aq)+H₂O(l)
ZnO(s)+2HCl(aq)→ZnCl₂(aq)+H₂O(l)
ZnO(s)+2NaOH(aq)→Na₂ZnO₂(aq)+H₂O(l)