Question

Why is Aluminum oxide considered as amphoteric oxide?

Answer 1

Amphoteric oxides

• Amphoteric oxides are metal oxides that react with both acids and bases to form salts and water.
• Lead oxide and zinc oxide are two examples of amphoteric oxides.
• Amphoteric species may either donate or accept a proton.

Aluminum oxide

• Aluminum oxide $\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$ is a metal with a lower electropositive value.
• It is an amphoteric oxide because it reacts with acids and bases to form salts and water.
• Reaction of ${\mathrm{Al}}_2{\mathrm{O}}_3$ with a base as follows:

${\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+6\mathrm{HCl}\left(\mathrm{aq}\right)\to 2{\mathrm{AlCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

• Reaction of ${\mathrm{Al}}_2{\mathrm{O}}_3$ with a base as follows:

${\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)\to 2{\mathrm{NaAlO}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$