Question

Two beakers, one containing 20ml of a 0.05 M aqueous solution of a non volatile, non-electrolyte and the other, the same volume of 0.03 M aqueous solution of $NaCl$, are placed side by side in a closed enclosure. What are the volumes in the two beakers when equilibrium is attained? Volume of the solution in the first and second beaker are respectively.

• A. 21.8 ml and 18.2 mL
• B. 18.2 mL and 21.8 mL
• C. 20 mL and 20 mL
• D. 17.1 mL and 22.9 mL

Answer 1

The correct option is A 21.8 ml and 18.2 mL

$\begin{array}{cc}\text{Moles of the solute in first beaker}& =\frac{0.05\times 20}{1000}\\ & =0.001\end{array}$

$\begin{array}{cc}\text{Moles of Solute in other beaker}& =\frac{2\times 0.03\times 20}{1000}\\ & =0.0012\end{array}$

$\begin{array}{c}\text{Concentration of second beaker is higher than}\\ \text{the first beaker so water flows from}\\ \text{1st beaker to second . Let '}{v}^{\prime }\text{volume of}\\ \text{water flows from first to second beaker}\\ \frac{0.001}{20-v}=\frac{0.0012}{20+v}\Rightarrow v=1.8ml\end{array}$

$\begin{array}{c}\text{Volume of 1st beaker}=20-1.8=18.2\\ \text{Volume of}2\text{nd beaker}=20+1.8=21.8ml\\ \text{Hence option}A\text{is correct}\end{array}$