Q43 / 150 · MHT CET 2021 (20 Sep Shift 2) · Chemistry

If vapour pressure of pure solvent and solution are 240 and 216 $\mathrm{mm} \mathrm{Hg}$ respectively then mole fraction of solvent in solution is

  • Correct answer
    A
    0.9
  • B
    0.1
  • C
    0.6
  • D
    0.4

Solution

$$ \begin{aligned} & \mathrm{P}_1=216 \mathrm{~mm} \mathrm{Hg} . \mathrm{P}_1^0=240 \mathrm{~mm} \mathrm{Hg} \\ & \Delta \mathrm{P}=\mathrm{P}_1^0-\mathrm{P}_1=240-216=24 \mathrm{~mm} \mathrm{Hg} \\ & \text { Now, } \frac{\Delta \mathrm{P}}{\mathrm{P}_1^0}=\mathrm{x}_2 \\ & \therefore \mathrm{x}_2=\frac{24 \mathrm{mmHg}}{240 \mathrm{mmHg}}-0.1 \end{aligned} $$ Hence, mole fraction of solvent, $\mathrm{x}_1=1-\mathrm{x}_2=1-0.1=0.9$

Hence, the correct answer is option: 'A'.

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