Question

A solution of an unknown nonvolatile nonelectrolyte was prepared by dissolving 0.250 g of the substance in 40.0 g of ccl4. the boiling point of the resultant solution was 0.357oc higher than that of the pure solvent. calculate the molar mass of the solute. (kb = 5.02oc/m)

Answer 1

Answer : The molar mass of the solute will be 87.90 g/mol.

Explanation : We know the formula for elevation in boiling point, which is

Δt = i$K_{b}$m

given that, Δt = 0.357, $K_{b}$ = 5.02 and mass of $CCl _{4}$ = 40,

on substituting the value we get,
0.357 = (1) X (5.02) X (x/ 0.044), on solving we get x = 2.844 X$10^{-3}$. 
Now, 0.250/ 2.844 X$10^{-3}$ = 87.90 g/mol. which is the weight of unknown component.