The Correct decreasing order of solubility of the following alcohols in water is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → IV > II > III > I
Alcohols dissolve in water because their –OH groups form hydrogen bonds with water. Solubility increases with the number of –OH groups and decreases as the hydrocarbon (hydrophobic) part grows. Compare the –OH groups per carbon:
IV. Glycerol, \( \ce{HOCH2-CH(OH)-CH2OH} \) — three –OH on three carbons: first (most soluble).
II. Ethane-1,2-diol, \( \ce{HOCH2-CH2OH} \) — two –OH on two carbons: second.
III. Propane-1,3-diol, \( \ce{HOCH2-CH2-CH2OH} \) — two –OH, but an extra \( \ce{CH2} \) group: third.
I. Ethanol, \( \ce{CH3CH2OH} \) — only one –OH: last (least soluble of the four).
NCERT (2026-27 edition):
Solubility – “Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with water molecules as shown. The solubility decreases with increase in size of alkyl/aryl (hydrophobic) groups. Several of the lower molecular mass alcohols are miscible with water in all proportions.”