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NEET CHEMISTRYSolutionsEasy

Question

The depression in freezing point of 0.01 M aqueous solutions of urea, sodium chloride and sodium sulphate is in the ratio of:

A

1 : 1 : 1

B

1 : 2 : 3

C

1 : 2 : 4

D

2 : 2 : 3

Step-by-Step Solution

Depression in freezing point (ΔTf\Delta T_f) is a colligative property proportional to the number of solute particles in the solution. It is calculated using the formula ΔTf=i×Kf×m\Delta T_f = i \times K_f \times m, where ii is the van't Hoff factor.

Since the solutions are dilute (0.01 M) and the solvent is the same, we assume molality is proportional to molarity and KfK_f is constant. Thus, the ratio of ΔTf\Delta T_f depends only on the van't Hoff factor (ii):

  1. Urea: A non-electrolyte, does not dissociate. i=1i = 1.
  2. Sodium Chloride (NaClNaCl): A strong electrolyte, dissociates as NaCl→Na++Cl−NaCl \rightarrow Na^+ + Cl^-. It gives 2 ions, so i=2i = 2.
  3. Sodium Sulphate (Na2SO4Na_2SO_4): A strong electrolyte, dissociates as Na2SO4→2Na++SO42−Na_2SO_4 \rightarrow 2Na^+ + SO_4^{2-}. It gives 3 ions, so i=3i = 3.

The ratio of depression in freezing point is 1:2:31 : 2 : 3.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Solutions. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYSolutionsdepressionfreezingaqueoussolutionssodium

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