JEE Main · 2025 · Shift-ImediumEC-134

The molar conductivity of a weak electrolyte when plotted against the square root of its concentration, which of the…

Electrochemistry · Class 12 · JEE Main Previous Year Question

Question

The molar conductivity of a weak electrolyte when plotted against the square root of its concentration, which of the following is expected to be observed?

Options
  1. a

    A small decrease in molar conductivity is observed at infinite dilution

  2. b

    A small increase in molar conductivity is observed at infinite dilution

  3. c

    Molar conductivity increases sharply with increase in concentration

  4. d

    Molar conductivity decreases sharply with increase in concentration

Correct Answerd

Molar conductivity decreases sharply with increase in concentration

Detailed Solution

Strategy: Recall the molar conductivity behavior for weak electrolytes. They do not follow a linear relationship with C\sqrt{C} and show a dramatic increase in Λm\Lambda_m only near the limit of infinite dilution.

Analysis:

  • As concentration (CC) increases, the °\degree of dissociation (α\alpha) for a weak electrolyte decreases rapidly according to Ostwald's Dilution Law.
  • Therefore, there is a sharp decrease in molar conductivity (Λm\Lambda_m) as concentration increases, starting from the near-infinite dilution state.
  • Option (d) correctly describes this steep curve behavior.

Answer: (d)\boxed{\text{Answer: (d)}}

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