State Kohlrausch law of independent migration of ions.(b) Write Nernst equation to calculate electrode potential.

Answer:

(a) Kohlrausch law: at infinite dilution, when dissociation of the electrolyte is complete, each ion migrates independently of its co-ion and makes a definite contribution to the molar conductivity. So the molar conductivity at zero concentration is the sum of the limiting molar ionic conductivities of the cation and the anion: \(\Lambda_0 = n_+\lambda_+^0 + n_-\lambda_-^0\) (e.g. \(\Lambda_0(\text{NaCl}) = \lambda^0_{\text{Na}^+} + \lambda^0_{\text{Cl}^-}\)).

(b) Nernst equation: for the electrode reaction Mⁿ⁺(aq) + ne^– → M(s),

\(E = E^\circ - \dfrac{2.303RT}{nF}\log_{10}\dfrac{1}{[\text{M}^{n+}]}\); at 298 K, \(E = E^\circ - \dfrac{0.0592}{n}\log_{10}\dfrac{1}{[\text{M}^{n+}]}\).