JEE Main · 2024 · 09 Apr 2024 · Shift 2 · Solutions

The vapour pressure of pure benzene and methyl benzene at

2 7^{\circ} C

is given as 80 Torr and 24 Torr, respectively. The mole fraction of methyl benzene in vapour phase, in equilibrium with an equimolar mixture of those two liquids (ideal solution) at the same temperature is ____

\times 1 0^{- 2}

(nearest integer)

Answer: 23

Solution

For an equimolar (ideal) mixture,

x_{b e n z e n e} = x_{t o l u e n e} = 0.5

in the liquid phase.

Partial pressures:

p_{b e n z e n e} = 0.5 \times 80 = 40

Torr;

p_{t o l u e n e} = 0.5 \times 24 = 12

Torr.

y_{t o l u e n e} = \frac{p _{t o l u e n e}}{p _{t o t a l}} = \frac{12}{40 + 12} = \frac{12}{52} = 0.2308 \approx 23 \times 1 0^{- 2}

JEE Main · 2024 · 09 Apr 2024 · Shift 2 · Integer answer

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