A 0.2% aqueous solution of a non-volatile solufe exerts a vapour pressure of
1.004 bar at 100C. What is the molar mass of the solute?
Vapour pressure of the solution at normal boiling point (p1) = 1.004 bar
Vapour pressure of pure water at normal boiling point 
Mass of solute, (w2) = 2 g
Mass of solvent (water), (w1) = 98 g
Molar mass of solvent (water), (M1) = 18 g mol−1
According to Raoult’s law,
= 41.35 g mol−1
Hence, the molar mass of the solute is 41.35 g mol−1.