Calculate the freezing point of the solution when 31 g of ethylene glycol (C2H6O2) is dissolved in 500 g of water.
(Kf for water = 1.86 K kg mol–1)
The freezing point of pure water is 273.15 K. On dissolving ethylene glycol, freezing point, being a colligative property, will be lowered.
We are given that
Kf for water=1.86 K kg mol−1
Mass of solute, ws=31 g
Molar mass of solute, Ms = 12 × 2 + 1 × 6 + 16 × 2
= 62 g mol−1
Mass of water, W=500 g
= 1.86 K
Hence, the freezing point of the solution,
Tf = 273.15 K−1.86 K
= 271.29 K