Which of the following carbonyl compounds is a gas at room temperature?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Methanal
Methanal (HCHO), the smallest aldehyde, is a gas at room temperature. Ethanal is already a volatile liquid, and the other aldehydes and ketones, such as propanal and propanone, are liquids or solids.
NCERT (2026-27 edition):
8.3 Physical Properties – “Methanal is a gas at room temperature. Ethanal is a volatile liquid. Other aldehydes and ketones are liquid or solid at room temperature.”