Assertion (A): Anilinium chloride is more acidic than ammonium chloride.
Reason (R): Anilinium ion is more resonance stabilised than aniline.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Assertion is correct but the Reason is incorrect.
In aniline the lone pair on nitrogen is in conjugation with the benzene ring. When aniline accepts a proton, this lone pair is used in the new N–H bond of the anilinium ion, \( \ce{C6H5NH3^+} \), and is no longer in conjugation with the ring.
Assertion (A): Anilinium chloride is more acidic than ammonium chloride. — True. Aniline is more stable than its cation, so it accepts a proton less readily and is a weaker base than ammonia. The weaker the base, the more readily its conjugate acid gives up the proton, so \( \ce{C6H5NH3^+} \) is a stronger acid than \( \ce{NH4^+} \):
\( \displaystyle \ce{C6H5NH3^+ <=> C6H5NH2 + H^+} \)
Reason (R): Anilinium ion is more resonance stabilised than aniline. — False. It is the other way round: aniline has five resonating structures and the anilinium ion only two, so aniline is the more resonance-stabilised species.
NCERT (2026-27 edition):
(b) Arylamines versus ammonia – “… If you write different resonating structures of aniline, you will find that aniline is a resonance hybrid of the following five structures.”
“On the other hand, anilinium ion obtained by accepting a proton can have only two resonating structures (kekule).”
“We know that greater the number of resonating structures, greater is the stability. Thus you can infer that aniline (five resonating structures) is more stable than anilinium ion. Hence, the proton acceptability or the basic nature of aniline or other aromatic amines would be less than that of ammonia.”