Methanol (CH3OH), ethanol (C2H5OH) and propanol (C3H7OH) belong to the same homologous series. By how much do the molecular masses of any two successive members differ? (Atomic masses: C = 12 u, H = 1 u, O = 16 u)
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 14 u
In a homologous series, successive members have the same functional group and differ by one \(\mathrm{CH_2}\) unit.
Mass of \(\mathrm{CH_2}=12+2\times1=14\,\mathrm{u}\)
Check: methanol \(=32\,\mathrm{u}\), ethanol \(=46\,\mathrm{u}\), propanol \(=60\,\mathrm{u}\); each step is \(14\,\mathrm{u}\)