Question

A solution containing $10.2g$ glycerine per litres is isotonic with a $2$% solution of glucose. What is the molecular mass of glycerine?

• A. $91.8g$
• B. $1198g$
• C. $83.9g$
• D. $890.3g$

Answer 1

Answer: (A)

$91.8g$

Since both solutions are isotonic so,

${\Pi }_1={\Pi }_2$ {osmotic pressure same}

$C_{1}RT=C_{2}RT$

$C_1=C_2$

$\frac{10.2}{Mw\times 1}=\frac{2\times 1000}{100\times 180}$ {$2$% glucose $=$ $2g$ in $100$ ml solution}

$\frac{10.2\times 100\times 180}{2000}=Mw\Rightarrow$

Molecular weight of glycerin $=91.8g$