question_answer 27)

 An aqueous solution of 2 percent of non-volatile solute exerts a pressure of 1.004 bar at the boiling point of the solvent. What is the molecular mass of the solute?

Answer:

Vapour pressure of pure water at the boiling point, p° = 1 atm = 1.013 bar Vapour pressure of solution, ps = 1.004 bar Mass of solute, w2 = 2 g Mass of solution = 100 g Mass of solvent, w1, = 98 g Applying Raoult's law for dilute solution (being 2%) or = 41.35g mol?1.