Question

A solution containing $10gperd{m}^3$ of urea (molecular mass $=60gmo{l}^{-1})$ is isotonic with a $5\%$ solution of a non-volatile solute. The molecular mass of this non-volatile solute is

Answer 1

Isotonic solutions are solutions which have same concentration, i.e., molarity.

$⟹$ Molarity of urea = $\left(\frac{10}{60}\right)\times \frac{1000}{10000}=\frac{1}{60}$

Molarity of non-volatile solute =$\left(\frac{5}{6M}\right)\times \frac{1000}{100}=\frac{50}{M}$

$⟹\frac{50}{M}=\frac{1}{60}$

Molar mass of the non-volatile solute = 3000 g