Question

Give reasons for the following:
(a)The pH of aqueous NaCl increases when it is electrolyzed.
(b) Unlike dry cell, mercury cell has a constant cell potential through its lifetime.
(c) Conductivity of solution decreases with dilution.

Hint:

Remember that the conductivity of a solution depends on the number of ions present, which decreases with dilution.

Answer 1

(a) During the electrolysis of NaCl, chlorine gas is released at the anode and hydrogen gas at the cathode. The hydrogen ions at the cathode are reduced, leading to an increase in the pH of the solution.
(b) In a mercury cell, the anode and cathode are made of mercury, which acts as a stable electrode material. The reaction at the electrodes does not cause significant changes in the electrode potential, so the cell maintains a constant potential throughout its lifetime.
(c) As the concentration of ions in a solution decreases with dilution, the number of charge carriers also decreases, leading to a decrease in conductivity.