Q36 / 160 · AP EAMCET 2014 · Chemistry

The molar mass of a solute $X$ in $\mathrm{g} \mathrm{mol}^{-1}$, if its $1 \%$ solution is isotonic with a $5 \%$ solution of cane sugar (molar mass $=342 \mathrm{~g} \mathrm{~mol}^{-1}$ ), is

Correct answer
A
$68.4$
B
$34.2$
C
$136.2$
D
$171.2$

Solution

For isotonic solutions $$ \begin{aligned} & \frac{W_1}{V_1 m_1}=\frac{W_2}{V_2 m_2} \\ & \frac{W_1}{V_1}=1, \frac{W_2}{V_2}=5 \\ & m_1=\text { ?, } m_2=342 \\ & \therefore \quad \frac{1}{m_1}=\frac{5}{342} or\\ & m_1=\frac{342}{5} or \\ & m_1=68.4=X \\ & \end{aligned} $$

Hence, the correct answer is option: 'A'.

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