Kohlrausch law of independent migration of ion is applicable to
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → To both - strong and weak electrolytes
The law is about limiting molar conductivity (at infinite dilution), where every electrolyte, strong or weak, is completely dissociated and each ion moves independently. For example:
\( \displaystyle \Lambda^\circ_m(\ce{CH3COOH}) = \lambda^\circ_{\ce{H+}} + \lambda^\circ_{\ce{CH3COO-}} \)
This is how Λ°m of a weak electrolyte, which cannot be found by extrapolation, is obtained from the values for strong electrolytes.
Why the other options are incorrect
Option (1) Only to weak electrolytes at a certain concentration — Incorrect. The law holds at infinite dilution, not at a finite concentration, and it is not limited to weak electrolytes.
Option (2) Only to strong electrolytes at all concentrations — Incorrect. It applies to weak electrolytes as well, and only at infinite dilution.
Option (4) To non-electrolytes — Incorrect. Non-electrolytes give no ions, so they have no ionic conductivity.
NCERT (2026-27 edition):
Variation of Conductivity and Molar Conductivity with Concentration – …
