Chemistry – Acids, bases and salts - Oxides | e-Consult

Amphoteric oxides are oxides that exhibit both acidic and basic properties. This means they can react with both acids and bases to form a salt and water. The term 'amphoteric' literally means 'having two different forms' (from the Greek 'amphos' meaning both and 'terikos' meaning form). In the context of oxides, it refers to their ability to react with both acidic and basic reagents.

Two examples of amphoteric oxides are aluminium oxide (Al₂O₃) and zinc oxide (ZnO).

Reaction with Hydrochloric Acid (HCl):

• Aluminium oxide reacts with hydrochloric acid to form aluminium chloride and water. The aluminium ion (Al³⁺) reacts with the hydrogen ions (H⁺) from the acid.
• Zinc oxide reacts with hydrochloric acid to form zinc chloride and water. The zinc ion (Zn²⁺) reacts with the hydrogen ions (H⁺) from the acid.

Balanced chemical equations:

1. Al₂O₃(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂O(l)
2. ZnO(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l)