JEE Main 2026 Apr 4 Shift 2, Chemistry Q4: Colligative Properties

JEE Main2026Apr 4, Shift 2Chemistry

At 27°C, 0.1 M, 1 L K $_{4}$ [Fe(CN) $_{6}$ ] aqueous solution and 0.1 M, 1 L FeCl $_{3}$ aqueous solution are placed in a container separated by a semi permeable membrane AB. Assume complete dissociation of both the solutes. Which of the following statement is correct?

A
Blue color is formed on both sides.
B
Ionic solutes in aqueous solution can pass through semi-permeable membrane.
C
Solution on side 'y' is hypotonic.
D
To cause the reverse flow of solvent during osmosis, external pressure (any value) should be applied to side 'x'.

Solution

A semi-permeable membrane allows only solvent (water) to pass, not the dissociated ions.

van't Hoff factors (complete dissociation): K $_{4}$ [Fe(CN) $_{6}$ ] $\to$ 4K $^{+}$ + [Fe(CN) $_{6}$ ] $^{4 -}$ , $i = 5$ . FeCl $_{3}$ $\to$ Fe $^{3 +}$ + 3Cl $^{-}$ , $i = 4$ .

Effective particle concentrations: side x $= 5 \times 0.1 = 0.5$ M; side y $= 4 \times 0.1 = 0.4$ M. So side x is hypertonic and side y is hypotonic.

Statement-wise:

(1) Wrong — Prussian blue forms only if Fe $^{3 +}$ and [Fe(CN) $_{6}$ ] $^{4 -}$ mix, which they cannot across an SPM.

(2) Wrong — ions cannot cross an SPM.

(3) Correct — side y has lower osmotic pressure and is hypotonic.

(4) Wrong — reverse osmosis requires external pressure on the hypertonic side (x), but the pressure must exceed the osmotic pressure difference, not "any value".

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JEE Main 2026 Apr 4 Shift 2, Chemistry Q4: Colligative Properties

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