On dissolving 0.5   g of a non-volatile non-ionic solute to 39   g of benzene, its vapor pressure…

On dissolving 0.5 g of a non-volatile non-ionic solute to 39 g of benzene, its vapor pressure decreases from 650 mm Hg to 640 mm Hg. The depression of freezing point of benzene (in K ) upon addition of the solute is _______
(Given data: Molar mass and the molal freezing point depression constant of benzene are 78 g mol-1 and 5.12 K kg mol-1, respectively)

Solution

ΔPPs=nsolutensolvent
650-640640=1×0.5×78M×39
Msolute=64 g
ΔTF=kf×m⇒
5.12×0.5×100064×39
ΔTf=1.0256

Asked in: JEE Advanced 2019 (Paper 1)

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