Question

Zinc oxide is said to have amphoteric nature, but Sodium oxide is not. Explain.

Answer 1

Part-1 Zinc oxide's nature

The oxide of metal like Zn(Zinc) is amphoteric as they react with both acid and the base. e.g. Zinc oxide (ZnO)

$$\begin{gathered} \mathrm{Amphoteric}\mathrm{oxide}+\mathrm{acid}\to \mathrm{Salt}+\mathrm{water} \\ \mathrm{Amphoteric}\mathrm{oxide}+\mathrm{base}\to \mathrm{Salt}+\mathrm{water} \end{gathered}$$

$$\begin{gathered} \mathrm{ZnO}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Zinc}\mathrm{oxide}\mathrm{Hydrochloric}\mathrm{acid}\mathrm{Zinc}\mathrm{chloride}\mathrm{Water} \\ \mathrm{ZnO}\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{ZnO}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Zinc}\mathrm{oxide}\mathrm{Sodium}\mathrm{hydroxide}\mathrm{Sodium}\mathrm{zincate}\mathrm{Water} \end{gathered}$$

Part-2 Sodium oxide's nature

• The oxide of Sodium (Na) is basic in nature and dissolves in nature to give hydroxide or alkali.
• They neutralize acid and don't react with base.

$$\begin{gathered} {\mathrm{Na}}_2\mathrm{O}+{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH} \\ \left(\mathrm{Sodium}\mathrm{oxide}\right)\left(\mathrm{Sodium}\mathrm{hydroxide}\right) \\ {\mathrm{Na}}_2\mathrm{O}+2\mathrm{HCl}\to 2\mathrm{NaCl} \\ \left(\mathrm{Sodium}\mathrm{oxide}\right)\left(\mathrm{Hydrochloric}\mathrm{acid}\right)\left(\mathrm{Sodium}\mathrm{chloride}\right) \end{gathered}$$

Hence, Zinc oxide is said to have amphoteric nature, but Sodium oxide is not