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JEE Main levelSingle correct optionDifficulty 2 of 3so041

At $373 K$ pure water has vapour pressure $760 mmHg$ . The vapour pressure of a solution of $6.0 g$ urea (molar mass $60$ ) in $180 g$ water (molar mass $18$ ) at the same temperature is

A $767.5 mmHg$
B $7.5 mmHg$
C $752.5 mmHg$
D $684.0 mmHg$

Answer: C

n_{urea} = 0.10

,

n_{water} = 10.0

.

p = x_{1} p^{0} = 760 \times 10.0/10.1 = 752.5 mmHg

. The value

7.5

is the lowering, not the new pressure.

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