Vapour pressure of solution

Vapour pressure: It is the pressure exerted by vapour on the upper layer of liquid at equilibrium between vapour and liquid. Factors affecting vapour pressure (A) Nature of liquid: Liquid with higher intermolecular attraction forces gives lower amount of vapour and hence lower vapour pressure and vice-versa. Thus order of vapour pressure at a particular temperature is Ethyl alcohol > Water > Ethylene glycol > Glycerine (B) Temperature: Vapour pressure increases with temperature of liquid. This is because, as temperature increases, kinetic energy of the molecules increases,  hence, more molecules leave the surface of the liquid and come into vapour phase. Clausius-Clapeyron equation is given to calculate the effect of temperature on vapour pressure. where P1 and P2 are the vapour pressures of the liquid at temperature T1 and T2 respectively and ΔHvap.  is enthalpy of vaporization of the liquid. Note: Vapour pressure of pure solvent > Vapour pressure of solution containing non-volatile solute . This is because non-volatile solute decrease the escaping tendency of the solvent molecules into the vapour phase.