Question

Which of the following oxides of nitrogen is a coloured gas ?

• A. $N_{2}O$
• B. $NO$
• C. $N_2{O}_5$
• D. $N{O}_2$

Answer 1

The correct option is D $N{O}_2$

Nitric oxide $\left(NO\right)$ appears as a colorless gas. Noncombustible but accelerates the burning of combustible material. Very toxic by inhalation and skin absorption.

Nitrogen dioxide $\left(N{O}_2\right)$ is a yellowish-brown liquid in its compressed form or reddish-brown gas.

Physical properties of nitrous oxide $\left(N_{2}O\right)$
Nitrous oxide is colourless in nature.
It exists in the gaseous state.
Nitrous oxide is a neutral molecule.
It is soluble in water.

Dinitrogen pentaoxide $\left(N_2{O}_5\right)$
It is a colourless crystalline solid. However, you cannot keep it under room temperature (at least in India) because its melting point is ${30}^o$.
Upon being melted at ${30}^o$, it transforms into a yellowish liquid.