Verified Solution • 2025–26 Session moderate

QJEEM23Chfa12: JEE Main 2023 Chemistry - Class 12 JEEM23Chfa12 Solution: The total pressure observed by mixing two liquids A and B is…

The total pressure observed by mixing two liquids A and B is 350 mm Hg when their mole fractions are 0.7 and 0.3 respectively.

The total pressure becomes 410 mm Hg if the mole fractions are changed to 0.2 and 0.8 respectively for A and B. The vapour pressure of pure A is __________ mm Hg. (Nearest integer)

Consider the liquids and solutions behave ideally.

Step-by-Step Verified Solution

Let V.PV . P of pure AA be PA0P_A^0

Let V.PV . P of pure BB be PB0P_B^0

When XA=0.7&XB=0.3\mathrm{X}_{\mathrm{A}}=0.7 \& \mathrm{X}_{\mathrm{B}}=0.3

Ps=350⇒PA0×0.7+PB0×0.3=350

When XA=0.2&XB=0.8\mathrm{X}_{\mathrm{A}}=0.2 \& \mathrm{X}_{\mathrm{B}}=0.8

Ps=410⇒PA0×0.2+PB0×0.8=410

Solving (i) and (ii)

PA0=314 mmHgPB0=434 mmHg∴Answer=314

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