Question

rate of evaporation decreases when common salt is added to water ?why?

Answer 1

When a non-volatile solute that is salt is added to a solvent that water, the vapour pressure of the resulting solution (salt solution) is less than the vapour pressure above the pure solvent (water). Thus rate of evaporation decreases.

Answer 2

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When a non-volatile solute that is salt is added to a solvent that water, the vapour pressure of the resulting solution (salt solution) is less than the vapour pressure above the pure solvent (water). Thus rate of evaporation decreases.