Exams › JEE Advanced › Chemistry
In which of the following phenomena does hydrogen bonding play a central role?
- Ice floats in water
- Higher Lewis basicity of primary amines than tertiary amines in aqueous solutions
- Formic acid is more acidic than acetic acid
- Dimerisation of acetic acid in benzene
Correct answer: Ice floats in water
Solution
Ice floating is caused by H-bond-driven open tetrahedral crystal structure. Primary amines are better proton acceptors in water partly because their NH2 can form more H-bonds for solvation. Acetic acid dimerises in non-polar benzene via double H-bonding between carboxyl groups. Formic acid's higher acidity than acetic acid is due to the inductive effect (no methyl group) — not H-bonding.
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