JEE Main · 2024 · Shift-IeasySOL-016

What happens to freezing point of benzene when small quantity of naphthalene is added to benzene?

Solutions · Class 12 · JEE Main Previous Year Question

Question

What happens to freezing point of benzene when small quantity of naphthalene is added to benzene?

Options
  1. a

    Increases

  2. b

    Remains unchanged

  3. c

    First decreases and then increases

  4. d

    Decreases

Correct Answerd

Decreases

Detailed Solution

Strategy:\n> According to Raoult's Law, the vapor pressure of a solution (PP) is the vapor pressure of the pure solvent (PP^\circ) multiplied by its mole fraction (xtextsolventx_{\\text{solvent}}).\n\nAnalysis:\n1. A non-volatile solute takes up space at the surface but doesn't contribute to vapor.\n2. Thus, the escape frequency of solvent molecules is reduced.\n3. P=xtextsolventPP = x_{\\text{solvent}} \cdot P^\circ. Since xtextsolvent<1x_{\\text{solvent}} < 1, the vapor pressure is always lowered.\n\ntextAnswer:(3)\boxed{\\text{Answer: (3)}}

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What happens to freezing point of benzene when small quantity of naphthalene is added to benzene? (JEE Main 2024) | Canvas Classes