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Raoult's Law

Easychemistry

An ideal binary liquid solution is prepared by mixing 3 mol of liquid A (vapour pressure 100 mmHg) with 2 mol of liquid B (vapour pressure 150 mmHg) at a given temperature. The total vapour pressure of the solution is:

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About This Question

Subject
chemistry
Chapter
solutions
Topic
raoult's law
Difficulty
Easy
Year
2025
Tags
Raoult's LawIdeal SolutionVapour Pressure

Solution

Correct Answer:

120 mmHg

For an ideal solution, Raoult's law applies: P_total = x_A·P°_A + x_B·P°_B. Mole fractions: x_A = 3/(3+2) = 0.6 and x_B = 2/(3+2) = 0.4. Therefore, P_total = (0.6 × 100) + (0.4 × 150) = 60 + 60 = 120 mmHg. The total vapour pressure is the sum of partial pressures of each component weighted by their mole fractions in the liquid phase. This is a direct application of Raoult's law for ideal solutions where no significant intermolecular interactions differ from pure components.

This easy difficulty chemistry question is from the chapter solutions, covering the topic of raoult's law. It appeared in the 2025 exam.

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