How is the vapour pressure of a solvent affected when a non volatile solute is dissolved in it?

Explanation

When solute is added to a solvent the vapor presure of the solvent (above the resulting solution) is lower than the vapor pressure above the pure solvent.
When a non volatile solute is added to sovent it reduces the escaping tendency of solvent molecule in to vapour phase because some of the solute particle occupy the surface and thus lower the vap pressure of solvent .This behaviour is shown by rault law
`P_(solvent)=X_(solvent)P_(solvent)^(0)`
Where: `P_(solvent)`is the vapour pressure of the solvent above the solution
`X_(solvent )` is the mole fraction of the solvent in the solution and
`P_(solvent)^(0)` is the vapor pressure of the pure solvent