Chemistry - Liquid Solution Question with Solution | TestHub

The molar concentration of urea solution $$=\frac{10g/d{m}^3}{\text{ Mol. wt. of urea }}=\frac{10}{60}\mathrm{M}=\frac{1}{6}\mathrm{M}$$ Molar concentration of $5\%$ nonvolatile solute $$\begin{array}{rl}& =\frac{50\mathrm{g}/{\mathrm{dm}}^3}{\text{ mol. wt. of non - volatile solute }}\\ & =\frac{50}{\mathrm{m}}\mathrm{M}\end{array}$$ Both solutions are isotonic to each other; therefore, $\frac{1}{6}=\frac{50}{m}$ $$m=50\times 6=300\mathrm{g}{\mathrm{mol}}^{-1}$$ Caution $10\mathrm{g}$ per ${\mathrm{dm}}^3$ of urea is isotonic with $5\%$ solution of a non-volatile solute. Hence, osmosis cannot occur between the two solutions. Thus, their molar concentrations are equal to each other.