Page 12 - Pharmaceutical Analytical Chemistry II - Pharm D Clinical- 07-PA202
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To obtain: E0Cd Cd(s)
Half-reaction: Cd2+ + 2e─
By measuring Ecell for the cell represented schematically as:
Pt, H2 (p = 1.00 atm) H+ (1.00 M) Cd2+ (1.00 M) Cd
E0cell = ─ 0.403 V, accordingly, E0 Cd2+/Cd = ─ 0.403 V
What does the Sign of Standard
Electrode potential, E0 imply?
E0Ag+/Ag = + 0.799 V E0Cd2+/Cd = ─ 0.403 V
When the half-cell of interest exhibits a positive potential relative
to SHE, i.e.
It will behave spontaneously as Cathode when the cell is
discharging,
The spontaneously reaction is REDUCTION
Ag+ + e─ Ag(s)
Acts as oxidizing agent, stronger oxidant than H+
Cell reaction: H2(g) + 2Ag+ 2H+ + 2Ag(s)
SHE acts as Anode
When the half-cell of interest exhibits a negative potential relative
to SHE, i.e.
It will behave spontaneously as Anode when the cell is
discharging,
The spontaneously reaction is OXIDATION
Cd(s) Cd2+ + 2e─
Acts as reducing agent, stronger reductant than H+
Cell reaction: Cd(s) + 2H+ Cd2+ + H2(g)
SHE acts as Cathode
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