The gas evolved when methylamine reacts with nitrous acid is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(N_2\)
Methylamine is a primary aliphatic amine; with nitrous acid it gives methanol and nitrogen gas:
\( \displaystyle \ce{NaNO2 + HCl -> HNO2 + NaCl} \)
\( \displaystyle \ce{CH3NH2 + HNO2 -> [CH3N2^+Cl^-] -> CH3OH + N2 ^ + HCl} \)
Why the other options are incorrect
Option (1) \(H_2\) — Incorrect. No hydrogen is set free; the H atoms end up in water, methanol and HCl.
Option (2) \(C_2H_6\) — Incorrect. Ethane would need two methyl groups to join, which does not happen in this reaction.
Option (4) \(NH_3\) — Incorrect. The nitrogen of the amine combines with the nitrogen of \( \ce{HNO2} \) and leaves as \( \ce{N2} \), not as ammonia.
NCERT (2026-27 edition):
Reaction with Nitrous Acid
