Question

Calculate the freezing point of water solution when, 724g of compound X (Mol Weight 62.07g), is mixed with 2605g of water (MW=18.02). Kf for water is 1.86ºC/m

Answer 1

The depression in freezing point for a solution of molality m is given by

Molality is defined as moles of solute per kilogram of solvent.

Amount of solute X = 724 g

Molecular weight = 62.07 g/mol

Hence, number of moles of solute =

Weight of solvent = 2605 g = 2.605 kg

Now molality of the solution is

Given that

We know that freezing point of pure water = 0 C.

Hence, after addition of X, freezing point of the solution will be