Write reactions to justify amphoteric nature of aluminium.

A substance is called amphoteric if it displays characteristics of both acids and bases. Aluminium dissolves in both acids and bases, showing amphoteric behaviour.

(i) $2 \mathrm{Al}_{(s)}+6 \mathrm{HCl}_{(a q)} \longrightarrow 2 \mathrm{Al}_{(a q)}^{3+}+6 \mathrm{Cl}_{(a q)}^{-}+3 \mathrm{H}_{2(g)}$

(ii) $2 \mathrm{Al}_{(s)}+2 \mathrm{NaOH}_{(a q)}+6 \mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow 2 \mathrm{Na}^{+}\left[\mathrm{Al}(\mathrm{OH})_{4}\right]_{(\text {(aq) }}^{-}+3 \mathrm{H}_{2(g)}$