Medium INTEGER +4 / -1 PYQ · JEE Mains 2024

$2.7 \mathrm{~kg}$ of each of water and acetic acid are mixed. The freezing point of the solution will be $-x^{\circ} \mathrm{C}$. Consider the acetic acid does not dimerise in water, nor dissociates in water. $x=$ ________ (nearest integer)

[Given: Molar mass of water $=18 \mathrm{~g} \mathrm{~mol}^{-1}$, acetic acid $=60 \mathrm{~g} \mathrm{~mol}^{-1}$

$${ }^{\mathrm{K}_{\mathrm{f}}} \mathrm{H}_2 \mathrm{O}: 1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$$

$\mathrm{K}_{\mathrm{f}}$ acetic acid: $3.90 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$

freezing point: $\mathrm{H}_2 \mathrm{O}=273 \mathrm{~K}$, acetic acid $=290 \mathrm{~K}$]

Answer (integer) 31

Solution

<p>$$\begin{aligned} & \text { Molality of acetic acid }=\frac{2700}{60} \times \frac{1}{2.7} \mathrm{~mol} / \mathrm{kg} \\ &=16.667 \\ & \Delta \mathrm{T}_{\mathrm{f}}=\mathrm{K}_{\mathrm{f}} \times 16.667 \\ &=1.86 \times 16.667 \\ &=31 \mathrm{~K} \end{aligned}$$</p>

About this question

Subject: Chemistry · Chapter: States of Matter · Topic: Gas Laws

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