Page 5 - Pharmaceutical Analytical Chemistry II - Pharm D Clinical- 07-PA202
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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) + 2Ag(s)
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