A 6% solution of glucose (molar mass =180 g mol^-1 ) is isotonic with 2.5% solution of an unknown organic substance. Calculate the molecular weight…

\(\displaystyle \pi_{\text {Glucose }}=\pi_{\text {Unknown }}\) \[\begin{array}{ll} \mathrm{C}_{\mathrm{G}}=\mathrm{C}_{\mathrm{U}} & \frac{W_{\mathrm{G}}}{\mathrm{M}_{\mathrm{G}}}=\frac{W_{\mathrm{U}}}{\mathrm{M}_{\mathrm{U}}} \\ \frac{6}{180}=\frac{2 \cdot 5}{\mathrm{M}_{\mathrm{U}}} & \\ \mathrm{M}_{\mathrm{U}=} \frac{2 \cdot 5 \times 180}{6} \mathrm{~g} \mathrm{~mol}^{-1} & =75 \mathrm{~g} \mathrm{~mol}^{-1} \end{array} \]