NCERT · Class 10 · Science · Metals and Non-metalsWhat are amphoteric oxides? Identify two amphoteric oxides from the following list: $\text{Na}2\text{O}$, $\text{Al}2\text{O}3$, $\text{CaO}$, $\text{ZnO}$. Write balanced chemical equations showing the reaction of one of these amphoteric oxides with both an acid and a base.

Definition of Amphoteric Oxides: Amphoteric oxides are metal oxides that react with both acids as well as bases to produce salt and water. They demonstrate both acidic and basic chemical behavior depending on the reacting substance.

Identification: From the given options, the two amphoteric oxides are:

1. Aluminium oxide ($\text{Al}_2\text{O}_3$)
2. Zinc oxide ($\text{ZnO}$)

Chemical Equations (using Aluminium oxide, $\text{Al}_2\text{O}_3$):

1. Reaction with an acid (Hydrochloric acid, $\text{HCl}$): In this reaction, aluminium oxide acts as a basic oxide. $$\text{Al}_2\text{O}_3\text{ (s)} + 6\text{HCl (aq)} \rightarrow 2\text{AlCl}_3\text{ (aq)} + 3\text{H}_2\text{O (l)}$$ (Aluminium chloride is formed as the salt.)

2. Reaction with a base (Sodium hydroxide, $\text{NaOH}$): In this reaction, aluminium oxide acts as an acidic oxide. $$\text{Al}_2\text{O}_3\text{ (s)} + 2\text{NaOH (aq)} \rightarrow 2\text{NaAlO}_2\text{ (aq)} + \text{H}_2\text{O (l)}$$ (Sodium aluminate is formed as the salt.)

Most non-metal oxides are acidic, whereas most metal oxides are basic. However, oxides of aluminium and zinc show dual character, making them essential examples of amphoteric oxides in inorganic chemistry.