Why is the vapous pressure of an aqueous solution of gulucose lower than that of water ?

Explanation

In pure liquid water, the entire surface of liquid is occupied by the molecules of water. When a non volatile solute, such as glucose is dissolved in water some of the surface is covered by non volatile glucose molecules. Therefore, the fraction of surface covered by the solvent molecules decreases. As a result number of solvent molecules escaping from the surface also gets reduced and consequently the vapour pressure of aqueous solution of glucose is reduced.