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JEE Main 202523 JanuaryEvening Shift
Exam
JEE Main
Year
2025
Date
23 January
Shift
Evening Shift
Subject
Chemistry
Chapter
Solutions

JEE Main 2025 · 23 January · Evening Shift · Chemistry · Solutions

When a non-volatile solute is added to the solvent, the vapour...

When a non-volatile solute is added to the solvent, the vapour pressure of the solvent decreases by 10 mm of Hg . The mole fraction of the solute in the solution is 0.2 . What would be the mole fraction of the solvent if decrease in vapour pressure is 20 mm of Hg ?

Options

  1. A0.8
  2. B0.4
  3. C0.2
  4. D0.6

Correct answer

D. 0.6

Step-by-step solution

∵P∘−P∝Xsolute  and ∵10∝0.2∴20∝0.4∴Xsolvent =1−Xsolute =1−0.4=0.6\begin{aligned} & \because \mathrm{P}^{\circ}-\mathrm{P} \propto \mathrm{X}_{\text{solute }} \\ & \text{ and } \because 10 \propto 0.2 \\ & \therefore 20 \propto 0.4 \\ & \therefore \mathrm{X}_{\text{solvent }}=1-\mathrm{X}_{\text{solute }} \\ & \quad=1-0.4 \\ & \quad=0.6\end{aligned}
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