Page 5 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102

Electrical Conduction in an electrochemical
cell

Electricity is conducted by:

• Electrons flow through the external conductor (wire)

• Within the two solutions; movement of anions and cations between

electrode compartments across the liquid junction. Anions move

towards anode and cations move towards cathode.

Classification of Electrochemical cell

Based on the SPONTANEITGYaolfvthaenielcectCroeclhlemical reactions:

Cells store electrical energy "e.g. Batteries"

The Redox reactions at the electrodes tend to proceed spontaneously

Chemical change (Redox reaction) → Electric current

Electrons flow from the anode to the cathode via an external conductor,
therefore, the anode is negative electrode and the cathode is positive
one

Anode Cu metal electrode /

CuSO4

Copper "half-reaction"

Oxidation

Cu(s) Cu2+ (aq) + 2e-

Cu2+ goes into aqueous solution

Decrease in the mass of Cu

electrode

Cathode Ag metal electrode/

AgNO3

Silver "half-reaction"

Reduction

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

Uncharged Ag atom deposits on

the silver electrode, increasing its

mass

Cell reaction Spontaneous

Cu(s) + 2Ag+(aq) Cu2+ (aq) 4 2Ag(s)
+