MCQEasyJEE 2023Abnormal Molar Mass & van't Hoff Factor

JEE Chemistry 2023 Question with Solution

Match List I with List II:

Two-column matching table for colligative properties. List I contains A. van't Hoff factor i, B. kf, C. Solutions with same osmotic pressure, D. Azeotropes. List II contains I. Cryoscopic constant, II. Isotonic solutions, III. Normal molar mass or Abnormal Mass, IV. Solutions with same composition of vapour above it.

Choose the correct answer from the options given below:

  • A

    A-III, B-I, C-II, D-IV

  • B

    A-II, B-I, C-III, D-IV

  • C

    A-III, B-II, C-IV, D-I

  • D

    A-I, B-III, C-II, D-IV

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: A matching question on colligative properties and related solution terms.

Find: The correct correspondence between List I and List II.

From the solution text:

  • ii (van't Hoff factor) is associated with abnormal molar mass, so A-III.
  • kfk_f is the cryoscopic constant, so B-I.
  • Solutions with the same osmotic pressure are isotonic solutions, so C-II.
  • Azeotropes have the same composition in liquid and vapour phases, so D-IV.

Thus the correct matching is A-III, B-I, C-II, D-IV.

Therefore, the correct option is A. The solution's states option C, but the extracted solution working supports A.

Common mistakes

  • Confusing kfk_f with a general equilibrium constant is incorrect because kfk_f here denotes the cryoscopic constant. Match it with depression of freezing point, not unrelated chemical constants.

  • Mistaking same osmotic pressure for azeotropic behaviour is incorrect because isotonic solutions are defined by equal osmotic pressure, whereas azeotropes refer to equal liquid and vapour composition.

  • Treating van't Hoff factor ii as a direct name for molar mass is incorrect because it is used to explain abnormal molar mass effects arising from association or dissociation. Match it with abnormal mass, not isotonic solutions.

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