Question

State the Kohlrausch law of independent migration of ions. Give an expression for the molar conductivity of acetic acid at infinite dilution.

Answer 1

Kohlrausch law of independent migration of ions

1. It states that “ Each ion migrates independently of its co-ion at infinite dilution and contributes to the total molar conductivity of an electrolyte on its own, regardless of the other ion it is associated with.”
2. It is represented by ${\mathrm{\lambda }}_{°}={\mathrm{\lambda }}_{°}^{+}+{\mathrm{\lambda }}_{°}^{-}$ where ${\mathrm{\lambda }}_{°}$ is molar conductivity of the electrolyte, ${\mathrm{\lambda }}_{°}^{+}$ is molar conductivity of cation, and ${\mathrm{\lambda }}_{°}^{-}$is molar conductivity of anion.

Molar conductivity of acetic acid

1. Molar conductivity can also be defined as the conducting power of all the ions that are formed by dissolving a mole of electrolyte in a solution.
2. Molar conductivity of ${\mathrm{CH}}_3\mathrm{COOH}$= Molar conductivity of ${\mathrm{CH}}_3{\mathrm{COO}}^{-}$ $+$Molar conductivity of ${\mathrm{H}}^{+}$
3. Expression: ${\mathrm{\lambda }}_0\left({\mathrm{CH}}_3\mathrm{COOH}\right)={\mathrm{\lambda }}_0\left({\mathrm{CH}}_3{\mathrm{COO}}^{-}\right)+{\mathrm{\lambda }}_0\left({\mathrm{H}}^{+}\right)$

Therefore, the molar conductivity of acetic acid (${\mathrm{CH}}_3\mathrm{COOH}$) is represented as ${\mathrm{\lambda }}_0\left({\mathrm{CH}}_3\mathrm{COOH}\right)={\mathrm{\lambda }}_0\left({\mathrm{CH}}_3{\mathrm{COO}}^{-}\right)+{\mathrm{\lambda }}_0\left({\mathrm{H}}^{+}\right)$