(a) Discuss, with the aid of diagrams, and with suitable examples, the chemistry (including half-cell reactions), construction and principles of the following electrode types:

(i) metal-metal-ion;

(ii) gas electrode;

(iii) metal-insoluble salt;

(iv) glass (membrane).

(b) Consider the following electrochemical cell:

                        Pt, H₂ (1 atm) | HCl (H₂O, 1m) || DCl (D₂O, 1m) | D₂ (1 atm), Pt

where D indicates the deuterium isotope, i.e. ²H.

(i) Show that the overall chemistry of the cell represents the exchange of a hydrogen atom and a deuterium ion as:

                                                        D⁺ + ½H₂ ® H⁺ + ½D₂

(ii) If E^o= 0.03696V for this cell at 298K, calculate the standard free energy of the exchange reaction (ΔG^o) and comment on both the magnitude of the result and the spontaneity of the reaction.

(iii) The temperature coefficient of the standard emf is -2.546 x 10^-4 V K^-1. Calculate the standard entropy change (ΔS^o) and comment briefly on it.