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Relative lowering of vapour pressure depends upon the mole fraction of solute. i.e., p° - p / p° = mole fraction of solute.

1. Relative lowering of vapour pressure depends upon the mole fraction of solute.
2. p° - p / p° = mole fraction of solute
3. Mole fraction of solute = 0.4
4. Depression of 2 × 0.2 mm Hg vapour pressure requires 2 × 0.2 mole fraction of solute.

Correct answer: p° - p / p° = mole fraction of solute

Solution

Raoult's law states that the relative lowering of vapor pressure is directly proportional to the mole fraction of the solute.

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