Question

State the Kohlrausch law of independent migration of ions. Why does the conductivity of a solution decrease with dilution?

Answer 1

Kohlrausch's law of independent migration of ions

Kohlrausch's law of independent migration of ions states that the limiting molar conductivity of an electrolyte can be represented by the sum of the individual contributions of the anion and cation of the electrolyte.

${\mathrm{\lambda }}^{°}={\mathrm{v}}_{+}{\mathrm{\lambda }}_{+}^{°}+{\mathrm{v}}_{-}{\mathrm{\lambda }}_{-}^{°}$ where

$$\begin{gathered} {\mathrm{\lambda }}^{°}=\mathrm{limiting}\mathrm{molar}\mathrm{conductivity} \\ {\mathrm{v}}_{+}{\mathrm{\lambda }}_{+}^{°}=\mathrm{conductivity}\mathrm{due}\mathrm{to}\mathrm{cations} \\ {\mathrm{v}}_{-}{\mathrm{\lambda }}_{-}^{°}=\mathrm{conductivity}\mathrm{due}\mathrm{to}\mathrm{anions} \end{gathered}$$

The conductivity of a solution decreases with dilution because the number of ions per unit volume of the solution decreases.