Question

Which of the following oxides are amphoteric?
A. ${\text{HgO}}$
B. ${\text{PbO}}$
C. ${\text{Pb}}{{\text{O}}_{\text{2}}}$
D. ${\text{Sn}}{{\text{O}}_{\text{2}}}$

Answer 1

Hint: The nature of the oxide is decided based on the product of hydrolysis. Metallic oxides behave as a base. Non-metallic oxides behave as acid. Amphoteric oxides behave as acid as well as a base.

Complete step by step answer:
Metallic oxides and hydroxide have metals and non-metallic oxides have non-metal.
The metal oxide on dissolving in water produces base. The non-metal oxide on dissolving in water produces acid.
The metal oxide reacts with acid, so they are base. The non-metal reacts with base, so they are acidic.
So, the nature of metallic oxides is basic and the nature of non-metallic oxides is acidic.
Some metallic oxides react with base and acid both are known as amphoteric oxides.
${\text{HgO}}$ is only stable in $ + 2$ oxidation state, so it is weakly amphoteric.
${\text{PbO}}$ reacts with hydrochloric acid and sodium hydroxide both, so it is amphoteric.
${\text{PbO}}\,{\text{ + }}\,{\text{HCl}} \to \,{\text{PbC}}{{\text{l}}_2}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}$
${\text{PbO}}\,{\text{ + }}\,{\text{NaOH}} \to \,{\text{N}}{{\text{a}}_{\text{2}}}{\text{Pb}}{\left( {{\text{OH}}} \right)_4}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}$
${\text{Pb}}{{\text{O}}_2}$ reacts with hydrochloric acid and sodium hydroxide both so, it is amphoteric.
${\text{Pb}}{{\text{O}}_2}\,{\text{ + }}\,{\text{HCl}} \to \,{\text{PbC}}{{\text{l}}_2}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\,{\text{ + }}\,{\text{C}}{{\text{l}}_2}$
${\text{Pb}}{{\text{O}}_2}\,\,{\text{ + }}\,{\text{NaOH}} \to \,{\text{N}}{{\text{a}}_{\text{2}}}{\text{Pb}}{\left( {{\text{OH}}} \right)_4}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}$
${\text{Sn}}{{\text{O}}_2}$ reacts with hydrochloric acid and sodium hydroxide both so, it is amphoteric.
${\text{Sn}}{{\text{O}}_2}\,{\text{ + }}\,{\text{HCl}} \to \,{{\text{H}}_{\text{2}}}{\text{SnC}}{{\text{l}}_{\text{6}}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}$
${\text{Sn}}{{\text{O}}_2}\,\,{\text{ + }}\,{\text{NaOH}} \to \,{\text{NaSn}}{{\text{O}}_3}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}$
So, amphoteric oxides are ${\text{PbO}}$,${\text{Pb}}{{\text{O}}_{\text{2}}}$ and ${\text{Sn}}{{\text{O}}_{\text{2}}}$.

Therefore, option (B),(C) and (D) ${\text{PbO}}$,${\text{Pb}}{{\text{O}}_{\text{2}}}$ and ${\text{Sn}}{{\text{O}}_{\text{2}}}$ are correct.

Note:
Amphoterism depends upon the oxidation state of the metal. As the oxidation state increases the amphoterism increases. Because of increasing positive charge the polarising power of the metal increases. The non-metal oxides are acidic. The metallic oxides are basic. Amphoteric oxides are both acidic as well as basic.