This vapour pressure of the
solution at a given temperature is found to
be lower than the vapour pressure of the
pure solvent at the same temperature In
the solution, the surface has both solute and
solvent molecules; thereby the fraction of the
surface covered by the solvent molecules gets
reduced Consequently, the number of
solvent molecules escaping from the surface
is correspondingly reduced, thus, the vapour
pressure is also reduced The decrease in the vapour pressure of solvent depends on the
quantity of non-volatile solute present in the solution, irrespective of
its nature