Page 11 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102
P. 11
Metal conductor: a piece of platinum that is platinized with finely
divided platinum (platinum black).
Electrolyte solution: aqueous acid solution, 1.00 M.
The solution is kept saturated with hydrogen by bubbling H2 gas at
1.00 atm pressure over the surface the electrode.
Platinum electrode is Inert electrode, i.e. it takes no part in
electrochemical reaction, it serves only as site where electrons are
transferred.
It is reversible: acts either as anode or cathode depending on the
half-cell to which it is coupled. H2 (g) E0 = 0.00 V
SHE reaction: 2H+ (aq) + 2e─
Schematic representation:
Pt, H2 (p = 1.00 atm) H+ (1.00 M)
The potential of SHE is assigned a value of 0.00 V at all temp
To obtain: E0Ag Ag(s)
Half-reaction: Ag+ + e─
By measuring Ecell for the cell represented schematically as:
Pt, H2 (p = 1.00 atm) H+ (1.00 M) Ag+ (1.00 M) Ag
E0cell = + 0.799 V, accordingly, E0Ag+/Ag = + 0.799 V
10
