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JEE Advanced levelSingle correct optionDifficulty 3 of 3so151

In an ideal binary solution with mole fraction of A equal to $0.40$ , the total vapour pressure is $600$ torr. The vapour pressure of pure A is $800$ torr. The vapour pressure of pure B (torr) is

A700.0
B280.0
C1000.0
D466.7

Answer: D

P = x_{A} P_{A}^{0} + x_{B} P_{B}^{0}

, so

p_{B} = 600 - 0.40 \times 800 = 280

torr. Since

x_{B} = 0.60

,

P_{B}^{0} = 280/0.60 = 466.7

torr. Dividing by 0.40 would wrongly use

x_{A}

.

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