Page 6 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102

Electrolytic Cell

Non-spontaneous Redox reaction is forced to occur at electrodes

It requires an external source of electrical energy for operation

Electric energy → Chemical change (Redox reaction)

The anode is connected to positive terminal of an external voltage source
while cathode to the negative terminal.
The electrons flow from negative terminal of voltage source (electron rich) to
cathode where reduction occurs,

Current is sustained by oxidation at anode producing electrons that flow to
the positive terminal of voltage source

Cathode Cu metal electrode/ CuSO4

Copper "half-reaction" Reduction
Cu2+ (aq) + 2e- Cu(s)

Anode Ag metal electrode/ AgNO3

Silver "half-reaction" Oxidation

Ag(s) Ag+(aq) + e-

The copper electrode is forced to
become cathode (Reduction) and
the silver electrode is forced to
become anode (Oxidation)

The opposite of the spontaneous cell
reaction is forced to occur

Cell reaction Non-spontaneous

2Ag(s) + Cu2+ (aq) 2Ag+(aq)
+ Cu(s)

Representing Cells Schematically

By convention, Cu/Cu SO4 Cathode
Zn/ZnSO4 Anode

ZnZn2+ (1.0 M)  Cu2+ (1.0 M)  Cu

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