What are amphoteric oxides? Give two examples of amphoteric oxides.
Amphoteric oxides are metal oxides that show both acidic and basic behaviour. These oxides can react with both acids as well as bases to produce salts and water.
Two examples of amphoteric oxides are:
- Aluminium oxide (Al₂O₃)
- Zinc oxide (ZnO)
For example, aluminium oxide reacts with hydrochloric acid to form aluminium chloride and water, and it also reacts with sodium hydroxide to form sodium aluminate and water.
Explanation
The chapter explains in Section 3.2.1 that some metal oxides, such as aluminium oxide and zinc oxide, show both acidic as well as basic behaviour. Such metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides. The reactions given are: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O and Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O.