(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 Eo= 0.03696V for this cell at 298K, calculate the standard free energy of the exchange reaction (ΔGo) 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 (ΔSo) and comment briefly on it.