Which from following compounds is NOT a mono carboxylic acid?

Find the void volume of bec unit cell in $\mathrm{cm}^3$ if volume of unit cell is $1.5 \times 10^{-22} \mathrm{~cm}^3$.

Which from following carbocations is least stable?

Identify compound Q in following reaction.

$$\mathrm{R}-\mathrm{OH}+\mathrm{Q} \longrightarrow \mathrm{R}-\mathrm{Cl}+\mathrm{HCl}+\mathrm{POCl}_3$$