Effective molality =0.6+1.6+0.4=2.6m As elevation in boiling point is a colligative property which depends on the amount of solute. So, to have same boiling point, the molality of two solutions should be same. Molality of non-electrolyte solution = molality of K4[Fe(CN)6]=2.6m Now, 18.1 weight per cent solution means 18.1g solute is present in 100g solution and hence, (100−18.1=)81.9g water.
Molality =
( Mass of solute / Molar mass of solute)
Mass of solvent (g)
×1000
Now, 2.6=
18.1/M
81.9/1000
where, M is the molar mass of non-electrolyte solute Molar mass of solute, M=85