What are the factors which affect the vapour pressure of a solution?

1.	What are the factors which affect the vapour pressure of a solution?
Answer» Solution : The vapour pressure of a solution depends on the FOLLOWING factors : (1) Nature of the solvent : The LIQUID molecules have a tendency to evaporate and form vapour above the liquid surface. This tendency depends on the intermolecular forces. The weaker are these intermolecular forces, more is the tendency of evaporation, and higher is the vapour pressure. These liquids are called volatile liquids. For example, alcohols, ethers, etc. (2) Nature of the solute : (a) Volatile solute : When a volatile solute like a volatile liquid is dissolved in another liquid solvent, the vapour pressure of the resulting solution is increased. e.g. Solution of an alcohol in water. (B) Nonvolatile solute : When a nonvolatile solute like glucose is dissolved in a liquid like water, the vapour pressure is LOWERED. (3) Concentration of a solution : As the concentration of a nonvolatile solute in the solution INCREASES, the vapour pressure decreases. If `P_(0)` and P are the vapour pressures of a pure solvent and a solution , then `P lt P_(0)` . (4) Temperature : Asthe tempertureincrease , vapourpressue of a liquid increase. Thetempertureat whichthe vapourpressuebecomes equalto theexternalpressureof oneatmosphere,represents the boiling pointof the liquid.

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