Question

A solution containing 9.5 g per $d{m}^3$ of $MgC{l}_2$ (molecular mass $95gmo{l}^{-1}$) is isotonic with a $5\%$ solution of a non-volatile solute. The molecular mass of solute is:

• A. $16.7gmo{l}^{-1}$
• B. $167gmo{l}^{-1}$
• C. $230gmo{l}^{-1}$
• D. $230mol{g}^{-1}$

Answer 1

The correct option is B $167gmo{l}^{-1}$

For isotonic solution ${\pi }_1={\pi }_2$
$i_1\times C_{1}RT=i_2\times C_{2}RT$
$3\times \frac{9.5}{95}=1\times \frac{5}{m\times {10}^{-1}}$
$m=\frac{5\times 100}{3}=167gmo{l}^{-1}$