Question

Freezing point of a $4\%$ aqueous solution of $X$ is equal to freezing point of $12\%$ aqueous solution of $Y$. If molecular weight of $X$ is $A$, then molecular weight of $Y$ is :

• A. A
• B. 3A
• C. 4A
• D. 2A

Answer 1

Answer: (B)

For same freezing point, molality of both solution should be same.
$m_{x} =m_{y}$
$ \frac{4\times1000}{96 \times M_{x}} = \frac{12\times1000}{88\times M_{y}} $
or, $ M_{y} = \frac{96\times12}{4 \times88} M_{x} = 3.27 A $
Closest option is 3A.