Liquid A and B form ideal solution for all compositions of A and B at 25 ° C . Two such solutions with 0.25 and 0.50 mole fractions of A have the total vapour pressures of 0.3 and 0.4 bar, respectively. What is the vapour pressure of pure liquid B in bar?

Chemistry · Solutions and Colligative Properties

JEE Advanced 2020 — Paper 2 — Question 29

Liquid $\mathbf{A}$ and $\mathbf{B}$ form ideal solution for all compositions of $\mathbf{A}$ and $\mathbf{B}$ at $25^{\circ} \mathrm{C}$ . Two such solutions with 0.25 and 0.50 mole fractions of $\mathbf{A}$ have the total vapour pressures of 0.3 and 0.4 bar, respectively. What is the vapour pressure of pure liquid $\mathbf{B}$ in bar?

Answer: 0.2

Numerical answer — enter this value.

Step-by-step solution

\begin{gathered} 0.3=p_{A}^{0} \times 0.25+p_{B}^{0} \times 0.75 ..(1) \end{gathered}

\begin{gathered} 0.4=p_{A}^{0} \times 0.50+p_{B}^{0} \times 0.50 ..(2) \end{gathered}

On solving, $\mathrm{p}_{\mathrm{B}}^{0}=0.20$ bar and $\mathrm{p}_{\mathrm{A}}^{0}=0.6$ bar

Answer key and solution verified before publishing.

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Exam: JEE Advanced 2020
Paper: Paper 2
Subject: Chemistry
Chapter: Solutions and Colligative Properties
Topic: Liquid in Liquid Solutions (Raoult's Law)