The freezing point of 53.70 g of a pure solvent is measured to be 48.55 ºc. when 2.07 g of an unknown solute (assume the van 't hoff factor = 1.) is added to the solvent the freezing point is measured to be 46.24 ºc. if the freezing point depression constant of the pure solvent is 7.17 ºc·kg solvent/mol solute calculate the molar mass of the solute.

)benzene and toluene form nearly ideal solutions. consider an equimolar solution of benzene and toluene. at 20 °c the vapour pressures of pure benzene and toluene are 9.9 kpa and 2.9 kpa, respectively. the solution is boiled by reducing the external pressure below the vapour pressure. calculate (i) the pressure when boiling begins, (ii) the composition of each component in the vapour, and (iii) the vapour pressure when only a few drops of liquid remain. assume that the rate of vaporization is low enough for the temperature to remain constant at 20 °c.