Question

Give two examples of each of the following oxides (a) Acidic oxides (b) Basic oxides (c) Amphoteric oxides (d) Neutral oxides.

State which of the following oxides i.e, (a) to (d)

(i) React with water to give a base

(ii) React with a base to give salt and water

(iii) React with acids and bases to give salt and water

Answer 1

(a) Acidic oxides

An acidic oxide is an oxide that when combined with water gives off an acid. Non-metallic oxides are acidic oxides.

Example: ${\mathrm{SO}}_2,{\mathrm{CO}}_2,{\mathrm{NO}}_2$, etc.

(b) Basic oxides

A basic oxide is an oxide that when combined with water gives off a base. Metallic oxides are basic oxides.

Example: ${\mathrm{Na}}_2\mathrm{O},{\mathrm{K}}_2\mathrm{O},\mathrm{CaO}$, etc.

(c) Amphoteric oxides

Metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides.

Example: $\mathrm{Zn},\mathrm{Pb},\mathrm{Al}$, etc.

(d) Neutral oxides

Neutral oxides show neither basic nor acidic properties and hence do not form salts when reacted with acids or bases.

Example: $\mathrm{NO},\mathrm{CO},{\mathrm{N}}_2\mathrm{O}$, etc.

(i) React with water to give a base

Basic oxides react with water to give a base.

Example: $$\begin{gathered} \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2 \\ \mathrm{Calcium}\mathrm{oxide}\mathrm{water}\mathrm{calcium}\mathrm{hydroxide} \end{gathered}$$

(ii) React with a base to give salt and water

Acidic oxides react with the base to give salt and water.

Example: $$\begin{gathered} {\mathrm{CO}}_2\left(\mathrm{g}\right)+2\mathrm{NaOH}\left(\mathrm{s}\right)\to {\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Carbon}\mathrm{dioxide}\mathrm{sodium}\mathrm{hydroxide}\mathrm{sodium}\mathrm{carbonate}\mathrm{water} \end{gathered}$$

(iii) React with acids and bases to give salt and water

Amphoteric oxides react with acids and based to give salt and water.

Example: $$\begin{gathered} {\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{AlCl}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Aluminium}\mathrm{oxide}\mathrm{Hydrochloric}\mathrm{acid}\mathrm{Aluminium}\mathrm{chloride}\mathrm{water} \\ {\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to {\mathrm{NaAlO}}_2\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Aluminium}\mathrm{oxide}\mathrm{sodium}\mathrm{hydroxide}\mathrm{sodium}\mathrm{aluminate}\mathrm{water} \end{gathered}$$