(a) Following reactions occur at cathode during the electrolysis of aqueous copper(II) chloride solution:

On the basis of their standard reduction electrode potential (E⁰) values, which reaction is feasible at the cathode and why?

(b) State Kohlrausch law of independent migration of ion. Write its one application.

(a) At cathode, higher positive values of E⁰ are only preferred. Hence, the below reaction is feasible. (+0.34V > 0.00V)

(b) Kohlrausch’s 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.

Explanation: At infinite dilution, when dissociation is complete, each ion makes a definite contribution towards molar conductance of electrolyte irrespective of the nature of the other ion with which it is associated and the molar conductance at infinite dilution for any electrolyte is given by the sum of contributions of two ions.

Applications:

• If λ⁰ for individual ions are known λ_m (molar conductivity) can be calculated.

• Once the λ⁰ for individual ions and λ_m (molar conductivity) are known, dissociation constant of weak electrolytes like acetic acid can be calculated easily.