Question

A solution containing $10.2g$ per glycerin per liter of a solution is found to be isotonic with $2$% solution of glucose molar mass $180$. Calculate the molar mass glycerin.

• A. 97.89 g/mol
• B. 183.24 g/mol
• C. 91.8 g/mol
• D. None of these

Answer 1

Answer: (C)

91.8 g/mol

${\Pi }_A{V}_A=n_{A}RT$ for glucose solution

$\Rightarrow {\Pi }_A\times 0.1=\frac{2}{180}\times RT⟶\left(1\right)$

${\Pi }_B{V}_B=n_{B}RT$ for glycerin solution

$\Rightarrow {\Pi }_B\times 1=\frac{10.2}{M_B}\times RT⟶\left(2\right)$

Since, ${\Pi }_A={\Pi }_B$

$\Rightarrow \frac{2}{180}\times \frac{RT}{0.1}=\frac{10.2}{M_B}\times \frac{RT}{1}$

$\Rightarrow M_B=91.8$gm ${mol}^{-1}$