Name three oxoacids of nitrogen. Write the disproportionation reaction of that oxoacid of nitrogen in which nitrogen is in $+3$ oxidation state?

Phosphorus has three allotropic forms -(i) white phosphorus (ii) red phosphorus and (iii) black phosphorus. Write the differences between white and red phosphorus on the basis of their structure and reactivity.

Assertion : ${\mathrm{N}}_2$ is less reactive than ${\mathrm{P}}_4$.
Reason : Nitrogen has more electron gain enthalpy than phosphorus.

Assertion : Both rhombic and monoclinic sulphur exist as ${\mathrm{S}}_8$ but oxygen exists as ${\mathrm{O}}_2$.
Reason : Oxygen forms $\mathrm{p\pi } – \mathrm{p\pi }$ multiple bond due to small size and small bond length but $\mathrm{p\pi } – \mathrm{p\pi }$ bonding is not possible in sulphur.

Assertion : $\mathrm{NaCl}$ reacts with concentrated ${\mathrm{H}}_2{\mathrm{SO}}_4$ to give colourless fumes with pungent smell. But on adding ${\mathrm{MnO}}_2$ the fumes become greenish yellow.
Reason : ${\mathrm{MnO}}_2$ oxidises $\mathrm{HCl}$ to chlorine gas which is greenish yellow.