In which electrochemical condition does the degree of dissociation (α) of a weak electrolyte approach unity (α = 1.0)?

Answer and explanation

Correct answer: C. At infinite dilution

  1. Step 1: According to Ostwald's dilution law for weak electrolytes: (when ).
  2. Step 2: As the solution is progressively diluted (), the interionic distance increases, and the fraction of ionized molecules increases continuously.
  3. Step 3: At infinite dilution (), ionization is 100% complete, so the degree of dissociation reaches unity (1.0).
  4. Step 4: Under this condition, the molar conductivity reaches its theoretical maximum, designated as the limiting molar conductivity ().
Answer
At infinite dilution (concentration approaching zero, C -> 0)
Why not the others: 'At standard molar concentration (C = 1.0 M)' weak electrolytes are only weakly dissociated (typically ); 'In completely non-polar organic solvents' dissociation is suppressed due to low dielectric constant; 'At the freezing point under high pressure' does not force complete ionization.

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