Question

Calculate the boiling point of a 1M aqueous solution (density 1.04 g mL-1) of Potassium chloride (Kb for water = 0.52 K kg mol-1,Atomic masses : K = 39 u, Cl = 35.5 u). Assume,Potassium chloride is completely dissociated in solution.

Answer 1

Molar mass of KCl = 39 + 35.5 = 74.35 g mol-1

As KCl dissociates completely, number of ions produced are 2.

Therefore, van't Hoff factor, i = 2

Mass of KCl solution = 1000 x 1.04 = 1040 g

Mass of solvent = 1040 - 74.5 = 965.5 g

= 0.9655 kg

Molality of the solution :