Question

Which one of the following metal oxides shows both acidic and basic characters?

• A. ${\mathrm{SO}}_2$
• B. ${\mathrm{K}}_2\mathrm{O}$
• C. ${\mathrm{Cu}}_2\mathrm{O}$
• D. ${\mathrm{Al}}_2{\mathrm{O}}_3$

Answer 1

The correct option is D

${\mathrm{Al}}_2{\mathrm{O}}_3$

Generally, metals react with Oxygen (${\mathrm{O}}_2$) and forms metal oxide because they are basic in nature.

Non-metals react with Oxygen (${\mathrm{O}}_2$) and form non-metal oxide because they are acidic in nature.

Some metallic oxides behave as amphoteric oxides because they display both the basic and acidic characters. Amphoteric oxides react with both acid and base and form salt and water.

Explanation for the correct option:

(D) Aluminium oxide (${\mathrm{Al}}_2{\mathrm{O}}_3$): Aluminium oxide (${\mathrm{Al}}_2{\mathrm{O}}_3$) is an amphoteric oxide because it can react with both acid and base to show both acidic and basic characteristics. The reactions of Aluminium oxide (${\mathrm{Al}}_2{\mathrm{O}}_3$) with an acid and a base are given below:

$\underset{\mathrm{Aluminium}\mathrm{oxide}}{{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{6\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Aluminium}\mathrm{chloride}}{2{\mathrm{AlCl}}_3\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

$\underset{\mathrm{Aluminium}\mathrm{oxide}}{{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Sodium}\mathrm{hydroxide}}{2\mathrm{NaOH}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Sodium}\mathrm{aluminate}}{2{\mathrm{NaAlO}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

Explanation for the incorrect option:

(A) Sulfur dioxide (${\mathrm{SO}}_2$): Sulfur dioxide (${\mathrm{SO}}_2$) is an acidic gas, therefore it does not show amphoteric nature.

(B) Potassium oxide (${\mathrm{K}}_2\mathrm{O}$): Potassium oxide (${\mathrm{K}}_2\mathrm{O}$) is a basic solid, therefore it does not show amphoteric nature.

(C) Copper oxide (${\mathrm{Cu}}_2\mathrm{O}$): Copper oxide (${\mathrm{Cu}}_2\mathrm{O}$) is a basic solid, therefore it does not show amphoteric nature.

Therefore, the correct option is (D).