PROSTAGLANDINS

DIFFERENT TYPES OF ELECTRODES
Types of electrodes
1)Metal – Metal ion half cell (𝑴𝒏+|𝑴) It consists
of a metal rod dipped in a solution of metal ion
 If act as cathode: 𝑀𝑛+ + 𝑛𝑒 → 𝑀(s)
 If act as anode: (𝑠) → 𝑀(𝑎𝑞)
 𝑛+ + 𝑛𝑒−
2) Gas electrode It consists of a solution containing
ions of gas species
 a. Hydrogen electrode: 𝑯+|𝑯𝟐 |𝑷𝒕 If act as
cathode: 𝐻 + + 𝑒 − → 1 2 ⁄ 𝐻2(𝑔) If act as anode: 1
2 ⁄ 𝐻2 → 𝐻 + + 𝑒 − b) Chlorine electrode: 𝑷𝒕 |𝑪𝒍𝟐(𝒈)
| 𝑪𝒍− in this 𝐶𝑙2 is passed over a Pt electrode which
is dipped in HCl
 Solution. If act as cathode:
1 2 ⁄ 𝐶𝑙2 + 𝑒 − → 𝐶𝑙− If act as anode: 𝐶𝑙− →

,  1 2 𝐶𝑙2 + 𝑒 − 3. Metal-Metal in soluble Salt – anion
It consists of metal electrode coated with the
insoluble salt of metal
 dipped in a solution containing ion common to the
anion of metal - Salt i) 𝐶𝑙−|𝐴𝑔𝐶𝑙|𝐴𝑔 ℎ𝑎𝑙𝑓𝑐𝑒𝑙𝑙 If act
as cathode
 2 𝐴𝑔𝐶(𝑠) ⇌ 𝐴𝑔(𝑎𝑞) + + 𝑒 − 𝐴𝑔(𝑎𝑞) + + 𝐶𝑙(𝑎𝑞) − ⇌
𝐴𝑔𝐶𝑙(𝑠) Net reaction: 𝐴𝑔𝐶𝑙 + 𝑒 − → 𝐴𝑔 + 𝐶𝑙−
If act as anode
 𝐴(𝑠) → 𝐴𝑔+ + 𝑒 − 𝐴𝑔++𝐶𝑙− ⇌ 𝐴𝑔𝐶𝑙 Net reaction:
𝐴𝑔 + 𝐶𝑙− → 𝐴𝑔𝐶𝑙 + 𝑒 −
ii), Calomel electrode 𝐶𝑙|𝐻𝑔2𝐶𝑙2 |𝐻𝑔|𝑃 if act as
cathode:
 𝐻𝑔2 2+ + 2𝑒 − → 2𝐻𝑔 𝐻𝑔2𝐶𝑙2 ⇌ 𝐻𝑔2 2+ + 2𝐶𝑙−
Net reaction: 𝐻𝑔2𝐶𝑙2 + 2𝑒 − ⇌ 2𝐻𝑔 + 2𝐶𝑙−
If act as anode:
 2𝐻𝑔 → 𝐻𝑔2 2+ + 2𝑒 − 𝐻𝑔2 2+ + 2𝐶𝑙− ⇌ 𝐻𝑔2𝐶𝑙2
Net Reaction: 2𝐻𝑔 + 2𝐶𝑙− → 𝐻𝑔2𝐶𝑙2 + 2𝑒 −