2019 H2 Chem P1 Q24 — Nitrogen Compound Solution

The answer is C (\(\text{C}_6\text{H}_5\text{NH}_2\), phenylamine).

P is only sparingly soluble in water but dissolves readily in cold HCl(aq), so P must be a base that reacts with \(\text{H}^+\) to give a soluble ionic salt. Cold acid is used, so no hydrolysis takes place.
Phenylamine is a liquid with a lone pair on N that accepts a proton:
\(\text{C}_6\text{H}_5\text{NH}_2 + \text{HCl} \rightarrow \text{C}_6\text{H}_5\text{NH}_3^+\text{Cl}^-\)
Phenylammonium chloride is ionic and dissolves; evaporating the solution leaves it as a crystalline solid.

• A is wrong: phenylethanone is a neutral ketone; it has no basic group, so it does not react with or dissolve in dilute HCl.
• B is wrong: benzamide is an amide; the N lone pair is delocalised onto the C=O group, so it is not available to accept a proton, and the amide is neutral. It is also a solid, not a liquid.
• D is wrong: phenol is weakly acidic, not basic, so it does not react with HCl(aq); it dissolves in NaOH(aq) instead.