What are amphoteric oxides? Give an example and write balanced chemical equations for its reaction with both an acid and a base.

Amphoteric oxides are metal oxides that react with both acids and bases to produce salt and water. An example is aluminium oxide (Al2O3). Reaction with acid: Al2O3(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2O(l) Reaction with base: Al2O3(s) + 2NaOH(aq) → 2NaAlO2(aq) + H2O(l) (or 2NaOH(aq) + Al2O3(s) + 3H2O(l) → 2Na[Al(OH)4](aq) depending on the form of sodium aluminate)