Question

Which of the following oxides of nitrogen is solid?
A.$N{O_2}$
B.${N_2}O$
C.${N_2}{O_3}$
D.${N_2}{O_5}$

Answer 1

Nitrogen atom possesses five valence electrons. Due to this reason it forms a variety of oxides, namely dinitrogen oxygen, nitrogen monoxide, dinitrogen trioxide, nitrogen dioxide and nitrogen pentoxide. Covalent compounds have low melting points and boiling points while ionic compounds have very high melting and boiling points.

Complete answer:
Ionic compounds consist of a cation and an anion which due to electrostatic forces of attraction form an ionic bond. The electrostatic forces are very strong and as a result, the compounds have very high melting points and boiling points and low vapour pressure.
In the given compounds, $N{O_2}$ (Nitrogen dioxide), ${N_2}O$ (dinitrogen oxygen) and ${N_2}{O_3}$ (dinitrogen trioxide), the bonds between nitrogen and oxygen are covalent and as a result, these gases exist as gases at room temperature.
However, the compound given in option B, that is, dinitrogen pentoxide, ${N_2}{O_5}$, is a solid at room temperature. Dinitrogen pentoxide is a rare compound that exists in two different structures depending on the conditions. In the solid state it exists as an ionic salt, nitronium nitrate made up of nitronium cation and nitrate anion. Due to ionic bonding, it exists as a colourless crystalline solid at room temperature.
When heated, it undergoes sublimation and forms covalently bonded dinitrogen pentoxide gas.

Thus, the correct option is D.

Note:
Dinitrogen pentoxide is an unstable and dangerous oxidizing agent. It is among one of the gases that result in the depletion of the ozone layer. It forms explosive mixtures with many organic compounds. On decomposition it yields toxic nitrogen dioxide gas.