Neet Solved Paper 2015 Question 22
Question: The boiling point of $ 0.2molk{g^{-1}} $ solution of X in water is greater than equimolal solution of Y in water. Which one of the following statements is true in this case?
Options:
A) X is undergoing dissociation in water.
B) Molecular mass of X is greater than the molecular mass of V.
C) Molecular mass of X is less than the molecular mass of V.
D) V is undergoing dissociation in water while X undergoes no change,
Show Answer
Answer:
Correct Answer: A
Solution:
Molality of solution X = molality of solution Y = 0.2mol/kg
We know that, elevation in the boiling point $ (\Delta T _{b}) $ of a solution is proportional to the molal concentration of the solution
i.e. $ \Delta T _{b}\propto m,or,\Delta T _{b}=K _{b}m $ where, m is the molality of the solution and $ K _{b} $ is molal boiling point constant or ebullioscopic constant.
$ \therefore $ By elevation in boiling point relation $ \Delta {\tau_b}=iK _{b}mor,\Delta {T_b}\propto i $ where, $ i $ is van’t Hoff is factor
Since, $ \Delta T _{b} $ , of solution X is greater than $ \Delta T _{b} $ of solution Y. (Observed colligative property is greater than normal colligative property).
$ \therefore $ $ i $ of solution $ X>i $ of solution Y
$ \therefore $ Solution X undergoing dissociation.
