Vapour Pressure of Liquid Solutions: The vapour pressure of a liquid solution is the pressure exerted by the vapours above a liquid solution in a closed container. The vapour pressure of a liquid solution is different from that of the pure solvent due to the presence of solute particles in the solution. The presence of solute particles reduces the number of solvent particles at the surface of the solution, which reduces the vapour pressure of the solution. The reduction in vapour pressure is proportional to the concentration of the solute particles.

Vapour Pressure of Liquid Solutions

The relationship between the vapour pressure of a solution and the concentration of solute particles can be described by Raoult’s law. Raoult’s law states that the vapour pressure of a solution is directly proportional to the mole fraction of the solvent in the solution. Mathematically, Raoult’s law can be expressed as:

Psolution = Xsolvent * Psolvent

where Psolution is the vapour pressure of the solution, Xsolvent is the mole fraction of the solvent in the solution, and Psolvent is the vapour pressure of the pure solvent.

Raoult’s law assumes that the solute does not react with the solvent and that the solute does not affect the intermolecular forces between solvent molecules. Raoult’s law is valid for solutions of nonvolatile solutes in volatile solvents.

The deviation from Raoult’s law can occur when the solute-solvent interactions are not the same as the solvent-solvent interactions. The deviation from Raoult’s law can be either positive or negative. A positive deviation from Raoult’s law occurs when the solute-solvent interactions are stronger than the solvent-solvent interactions, which results in a higher vapour pressure than predicted by Raoult’s law. A negative deviation from Raoult’s law occurs when the solute-solvent interactions are weaker than the solvent-solvent interactions, which results in a lower vapour pressure than predicted by Raoult’s law.

The study of the vapour pressure of liquid solutions is important in many fields, including chemical engineering, biochemistry, and materials science. It is used to determine the concentration of solutes in a solution and to understand the physical and chemical properties of the solutions.

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By Team Learning Mantras