A solution of non volatile solute is obtained by dissolving 2 g in 50 g benzene. Calculate the vapour…

A solution of non volatile solute is obtained by dissolving 2 g in 50 g benzene. Calculate the vapour pressure of solution if vapour pressure of pure benzene is 640 mmHg at $25^{\circ} \mathrm{C}$. [mol. mass of benzene $=78 \mathrm{~g} \mathrm{~mol}^{-1}$, mol. mass of solute $\left.=64 \mathrm{~g} \mathrm{~mol}^{-1}\right]$
  1. 600.21 mm Hg
  2. 604.52 mm Hg
  3. 608.64 mm Hg
  4. 612.83 mm Hg

Solution

$\begin{aligned} \quad \frac{\Delta \mathrm{P}}{\mathrm{P}^0}= & \frac{\mathrm{P}^0-\mathrm{P}}{\mathrm{P}^0}=\mathrm{x}_2=\frac{\mathrm{W}_2 \mathrm{M}_1}{\mathrm{~W}_1 \mathrm{M}_2} \\ \therefore \quad \frac{640-\mathrm{P}}{640} & =\frac{2 \times 78}{50 \times 64} \\ 640-\mathrm{P} & =640 \times 0.048 \\ \mathrm{P} & =640-31.2 \\ \mathrm{P} & =608.8 \mathrm{~mm} \mathrm{Hg}\end{aligned}$

Asked in: MHT CET 2024 (02 May Shift 1)

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