Here's why:
* Amphoteric oxides are metal oxides that can act as both acids and bases.
* Acids donate hydrogen ions (H+) in solution.
* Alkalis are bases that donate hydroxide ions (OH-) in solution.
Reaction with Acids:
When an amphoteric oxide reacts with an acid, it acts as a base, accepting hydrogen ions to form a salt and water.
Example:
Aluminum oxide (Al2O3) reacts with hydrochloric acid (HCl):
Al2O3 (s) + 6HCl (aq) → 2AlCl3 (aq) + 3H2O (l)
Here, aluminum chloride (AlCl3) is the salt formed.
Reaction with Alkalis:
When an amphoteric oxide reacts with an alkali, it acts as an acid, donating oxide ions (O2-) to form a salt and water.
Example:
Aluminum oxide (Al2O3) reacts with sodium hydroxide (NaOH):
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) → 2NaAl(OH)4 (aq)
Here, sodium aluminate (NaAl(OH)4) is the salt formed.
Common examples of amphoteric oxides:
* Aluminum oxide (Al2O3)
* Zinc oxide (ZnO)
* Lead oxide (PbO)
Therefore, amphoteric oxides like aluminum oxide react with both acids and alkalis to form salt water (and another salt).
