What do you understand by amphoteric oxides? Explain with the help of an example. [3 marks]

Metal oxides that can act as an acid as well as base in a reaction to produce a salt and water are called amphoteric metal oxides. [1 mark]
For example, oxides of aluminium and zinc are amphoteric in nature.

• Aluminium oxide on reaction with hydrochloric acid form aluminium chloride salt and water and thus, acts as a base in the reaction.

Aluminium oxide + Hydrochloric acid $\to$ Aluminium chloride + Water [1 mark]

• Aluminium oxide on reaction with sodium hydroxide form sodium aluminate salt and water and thus, acts as an acid.

Aluminium oxide + Sodium hydroxide $\to$ Sodium aluminate + Water [1 mark]