The vapour pressure of benzene at 90 ° C is 1020 torr. A solution of 15 g of a solute in 58.5 g benzene has a vapour pressure of 990 torr. The molecular weight of the solute is

Question

The vapour pressure of benzene at 90 ° C is 1020 torr. A solution of 15 g of a solute in 58.5 g benzene has a vapour pressure of 990 torr. The molecular weight of the solute is, 78.2, 204.2, 148.2, 226.6

MARKS App · Accepted Answer

Using Raoult's law for relative lowering of vapour pressure as follows P o - P s P o = w × M m × W Here P o = V P or pure solvent, P s = VP of solution or 1020 - 990 1020 = 5 × 78 m × 58.5 So m = 226.6 .

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