Question

Which of the following oxides is acidic in nature?
A. CO
B. ${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}$
C. ${\text{C}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{7}}}$
D. ${{\text{N}}_{\text{2}}}{\text{O}}$

Answer 1

Hint : Those oxides are acidic in nature which combine with water molecules to produce acidic species. Check which given species on reaction with water produces an acid.

Complete step by step solution :
Acidic oxides are those oxides which combine with water molecules to produce an acid. Thus we will carry out a chemical reaction with water for each given oxides. The oxide which will form acid on reacting with water will be acidic in nature.

When CO (carbon monoxide) reacts with water, hydrogen gas is released and carbon dioxide gas is also formed.
${\text{CO}} + {{\text{H}}_{\text{2}}}{\text{O}} \rightleftharpoons {{\text{H}}_{\text{2}}} + {\text{C}}{{\text{O}}_{\text{2}}}$

This shows that CO is not acidic in nature. CO is a neutral oxide which means it neither behaves as an acidic oxide not basic oxide. This is due to the equilibrium which lies in the left hand side of the reaction.

Aluminium oxide $\left( {{\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}} \right)$ acts as an amphoteric oxide. This means it has capability to behave as an acid and base as well.

When aluminium oxide reacts with hydrogen chloride (an acid), aluminium chloride $\left( {{\text{AlC}}{{\text{l}}_{\text{3}}}} \right)$ and water are formed.
${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}} + 6{\text{HCl}} \to 2{\text{AlC}}{{\text{l}}_{\text{3}}} + 3{{\text{H}}_{\text{2}}}{\text{O}}$

When aluminium oxide reacts with sodium hydroxide (a base) in the presence, sodium aluminate is formed, i.e., ${\text{Na}}\left[ {{\text{Al}}{{\left( {{\text{OH}}} \right)}_{\text{4}}}} \right]$
${\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}} + 2{\text{NaOH}} + 3{{\text{H}}_2}{\text{O}} \to 2{\text{Na}}\left[ {{\text{Al}}{{\left( {{\text{OH}}} \right)}_{\text{4}}}} \right]$

When chlorine heptoxide $\left( {{\text{C}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{7}}}} \right)$ reacts with water, perchloric acid $\left( {{\text{HCl}}{{\text{O}}_{\text{4}}}} \right)$ is formed.
${\text{C}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{7}}} + {{\text{H}}_{\text{2}}}{\text{O}} \to 2{\text{HCl}}{{\text{O}}_{\text{4}}}$

This shows that ${\text{C}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{7}}}$is acidic in nature as it produces perchloric acid on reaction with water.

Nitrous oxide (${{\text{N}}_{\text{2}}}{\text{O}}$) is a neutral oxide. The solution of ${{\text{N}}_{\text{2}}}{\text{O}}$ in water is neutral in nature. This is probably due to the following equilibrium which lies in the left hand side.

${{\text{N}}_2}{\text{O}} + {{\text{H}}_{\text{2}}}{\text{O}} \rightleftharpoons {{\text{H}}_{\text{2}}}{{\text{N}}_{\text{2}}}{{\text{O}}_{\text{2}}}$

Thus the correct option is C.

Note : Remember that there are different types of oxides such as acidic oxides, basic oxides, amphoteric oxides and neutral oxides. The treatment of acidic oxide with water produces an acid. . The treatment of basic oxide with water produces a base. Amphoteric oxide behaves as both acid and base. Neutral acid neither behaves as acid nor as base.