Question

A 1 molal K₄Fe(CN)₆ solution has a degree of dissociation of 0.4. Its boiling point is equal to that of another solution which contains 18.1 weight percent of a non electrolytic solute A. The molar mass of A is ....... u. (Round off to the Nearest Integer).

[Density of water = 1.0 g cm^–3]

Answer 1

Effective molality = 0.6 + 1.6 + 0.4 = 2.6m

For same boiling point, the molality of another solution should also be 2.6 m. Now, 18.1 weight percent solution means 18.1 gm solute is present in 100 gm solution and hence, (100 – 18.1 =) 81.9 gm water.

∴ Molar mass of solute, M = 85