Question
Which of the following are not correct?
A. For water, magnitude of $K_{b}$ is more than the magnitude of $K_{f}$.
B. The elevation in boiling point of water when a non-volative solute is added to it is larger in magnitude than its depression in freezing point.
C. Osmotic pressure measurement is preferred over any other colligative property to determine molar mass of proteins and polymers.
D. The dimerised form of benzoic acid in benzene is 
Choose the correct answer from the options given below:
Options
Solution
Sol. [Key Concept: For water $K_{b}(0.512) < K_{f}(1.86)$ so statements A and B are wrong, and the benzoic-acid dimer is H-bonded through both $- COOH$ groups so D's structure is wrong; only C (osmometry for macromolecules) is correct, hence A, B and D are not correct.]
(A) $K_{b}$ for water $= 0.512\frac{\ ^{\circ}C - Kg}{mol}$
$K_{f}$ for water $= 1.86\frac{\ ^{\circ}C - Kg}{mol}$
So, $K_{b} < K_{f}$ for water
(B) Since, $K_{b} < K_{f}$ so $\Delta T_{b} < \Delta T_{f}$ [same equimolal solution]
(C) Osmotic pressure is used to determine molar mass of protiens & polymers
(D) dimerised form of benzoic acid in benzene
option (A), (B) & (D) are incorrect
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