JEE Main 2025 Apr 4 Shift 2, Chemistry Q12: Colligative Properties

JEE Main2025Apr 4, Shift 2Chemistry

Consider the given data :

(a) $H C l (g) + 10 H_{2} O (l) \to H C l \cdot 10 H_{2} O$ $Δ H = - 69.01$ kJ mol $^{- 1}$

(b) $H C l (g) + 40 H_{2} O (l) \to H C l \cdot 40 H_{2} O$ $Δ H = - 72.79$ kJ mol $^{- 1}$

Choose the correct statement :

A
Dissolution of gas in water is an endothermic process
B
The heat of solution depends on the amount of solvent.
C
The heat of dilution for the HCl ( $H C l \cdot 10 H_{2} O$ to $H C l \cdot 40 H_{2} O$ ) is 3.78 kJ mol $^{- 1}$ .
D
The heat of formation of HCl solution is represented by both (a) and (b)

Solution

Both $Δ H$ values are negative, so dissolution is exothermic — option (1) is wrong.

The two processes differ only in the amount of solvent (10 vs 40 mol $H_{2} O$ ), yet give different $Δ H$ values ( $- 69.01$ vs $- 72.79$ kJ mol $^{- 1}$ ). This directly shows the heat of solution depends on the amount of solvent — option (2) is correct.

Heat of dilution = $Δ H_{(b)} - Δ H_{(a)} = - 72.79 - (- 69.01) = - 3.78$ kJ mol $^{- 1}$ (negative, not $+ 3.78$ ) — option (3) is wrong.

A heat of formation requires the reactants to be in their elemental forms; here HCl(g) is used, so neither equation represents a heat of formation — option (4) is wrong.

$∴$ The correct statement is (2).

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JEE Main 2025 Apr 4 Shift 2, Chemistry Q12: Colligative Properties

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