Electrochemistry · Question 34

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?

1. Molar conductivity increases sharply with increase in concentration.
2. Molar conductivity decreases sharply with increase in concentration.
3. A small increase in molar conductivity is observed at infinite dilution.
4. A small decrease in molar conductivity is observed at infinite dilution.

Answer

(2) Molar conductivity decreases sharply with increase in concentration.

Solution

As per NCERT, for a weak electrolyte (e.g. CH3COOH) m = m .

On dilution the degree of dissociation increases steeply, so m rises sharply at low concentration.

Conversely, m decreases sharply as the concentration increases; the plot of m vs c is a steep curve, not a straight line (unlike a strong electrolyte, where m decreases only slightly and linearly).

Answer: (2)