Identify the reagent used in the following reaction.

Benzoic acid $\xrightarrow{\text { Reagent }}$ Benzoyl chloride + Phosphorus oxychloride + Hydrogen chloride

If $\mathrm{E}^o{}\left(\mathrm{AI}_{(\mathrm{eq})}^{+3} \mid \mathrm{AI}_{(\mathrm{s})}\right)=-1.66 \mathrm{~V}$. What is potential of $\mathrm{Al}_{(\mathrm{s})} \longrightarrow \mathrm{Al}^{+3}(0 \cdot 1 \mathrm{M})+3 \mathrm{e}^{-}$at 298 K ?

A gaseous mixture of $\mathrm{O}_2$ and $\mathrm{CH}_4$ are in the ratio $1: 4$ by mass. Find the ratio of their molecules.

Calculate the relative lowering of vapour pressure of solution containing 3 g urea in 50 g water. [molar mass of urea $=60 \mathrm{~g} \mathrm{~mol}^{-1}$ ]