# A solution containing 8.6g per $dm^3$ of urea (molar mass = 60g $mol^{–1}$) was found to be isotonic with a 5 percent solution of an organic non-volatile solute. Calculate the molar mass of the latter (solute).

Let $M_2$ be the molar mass of the unknown solute
Molar concentration of urea solution =$\large\frac{50gdm^{-3}}{M_2}$
Thus $\large\frac{50g\;dm^{-3}}{M_2}=\frac{8.6g dm^{-3}}{60g mol^{-1}}$
$M_2=348.8gmol^{-1}$