JEE Main 2026 Apr 8 Shift 2, Chemistry Q4: Colligative Properties

JEE Main2026Apr 8, Shift 2Chemistry

Which of the following are not correct ?

A. For water, magnitude of $K_{b}$ is more than the magnitude of $K_{f}$ .

B. The elevation in boiling point of water when a non-volatile solute is added to it is larger in magnitude than its depression in freezing point.

C. Osmotic pressure measurement is preferred over any other colligative property to determine molar mass of proteins and polymers.

D. The dimerised form of benzoic acid in benzene is

Choose the correct answer from the options given below :

A
A and B only
B
A and D only
C
A, B and D only
D
A, C and D only

Solution

Evaluate each statement on its own merits.

A. False. For water, $K_{b} = 0.512$ K $\cdot$ kg/mol and $K_{f} = 1.86$ K $\cdot$ kg/mol; the cryoscopic constant is larger.

B. False. For an equimolal solute, $Δ T_{b} = K_{b} m$ and $Δ T_{f} = K_{f} m$ . Since $K_{f} > K_{b}$ , freezing-point depression exceeds boiling-point elevation in magnitude.

C. True. Proteins and polymers have large molar masses, so $Δ T_{b}, Δ T_{f}$ , and vapour-pressure lowering are too small to measure accurately. Osmotic pressure is appreciable even at low concentrations and is measured at room temperature, avoiding heat-induced denaturation.

D. False. The genuine benzoic acid dimer in benzene has a cyclic, doubly-H-bonded structure (two O–H $\dots$ O bonds in a closed ring), not the single-bridge form shown.

Incorrect statements: A, B, D.

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JEE Main 2026 Apr 8 Shift 2, Chemistry Q4: Colligative Properties

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