Kohlrausch law is related to which of the following term ?

The correct answer is Option (4) → Migration of ions

Kohlrausch’s law of independent migration of ions states that the limiting molar conductivity of an electrolyte is the sum of the individual contributions of its anion and cation, each ion migrating independently of the other:

    \( \displaystyle \Lambda_m^{\circ}=\nu_+\lambda_+^{\circ}+\nu_-\lambda_-^{\circ} \)

For example, \( \Lambda_m^{\circ}(\ce{NaCl})=\lambda^{\circ}(\ce{Na+})+\lambda^{\circ}(\ce{Cl-}) \). It is used to find Λ_m° of weak electrolytes and their degree of dissociation.

NCERT (2026-27 edition):
Variation of Conductivity and Molar Conductivity with Concentration – “Kohlrausch examined Λ°_m values for a number of strong electrolytes and observed certain regularities. … On the basis of the above observations he enunciated Kohlrausch law of independent migration of ions. The law states that limiting molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation of the electrolyte.”