The molar mass of a solute X in gmol^-1 . If it's 1% solution is isotonic with 5% solution of cane sugar (molar mass= 342 gmol^-1) is________Round off to nearest integer.

For isotonic solutions, π₁ = π₂
$\frac{{\mathrm{n}}_1\mathrm{RT}}{{\mathrm{V}}_1}=\frac{{\mathrm{n}}_2\mathrm{RT}}{{\mathrm{V}}_2}\Rightarrow \frac{{\mathrm{n}}_1}{{\mathrm{V}}_1}=\frac{{\mathrm{n}}_2}{{\mathrm{V}}_2}$
Thus, $\frac{{\mathrm{W}}_1}{{\mathrm{V}}_1{\mathrm{m}}_1}=\frac{{\mathrm{w}}_2}{{\mathrm{V}}_2{\mathrm{m}}_2},\frac{{\mathrm{W}}_1}{{\mathrm{V}}_1}=1,\frac{{\mathrm{W}}_2}{{\mathrm{V}}_2}=5$
$\begin{array}{l}{\mathrm{m}}_1=?,{\mathrm{m}}_2=342,\frac{1}{{\mathrm{m}}_1}=\frac{5}{342}\\ {\mathrm{m}}_1=\frac{342}{5}=68.4=\mathrm{x}\end{array}$
i.e. molar mass of solute x is 68.4 $\approx$ 68 g mol^-1