The molar volume of liquid benzene (density = 0.877 g mL^-1) increases by a factor of 2750 as it vaporises at 20^oC and that of liquid toluene (density = 0.867 g mL^-1) increases by a factor of 7720 at 20^oC. A solution of benzene and toluene at 20^oC has vapour pressure of 46.0 Torr. Find the mole fraction of benzene in the vapour above the solution.

What weight of the non-volatile solute, urea(NH₂ - CO - NH₂) needs to be dissolved in 100g of water, in order to decrease the vapour pressure of water by 25%? What will be the molality of the solution?

The degree of dissociation of calcium nitrate in a dilute aqueous solution, containing 7.0 g. of the salt per 100 gm of water at 100^oC is 70%. If the vapour pressure of water at 100^oC is 760 mm, calculate the vapour pressure of the solution.

The vapour pressure of pure benzene at a certain temperature is 640 mm Hg. A non-volatile non-electrolyte solid weighing 2.175 g is added to 39.0 g of benzene. The vapour pressure of the solution is 600 mm Hg. What is the molecular weight of the solid substance?