Electrochemistry involves redox reactions in galvanic cells that convert chemical energy to electrical energy. In a galvanic cell, oxidation occurs at the anode and reduction occurs at the cathode. A salt bridge completes the circuit between the two half cells and maintains electrical neutrality. When a zinc rod is used as the anode in a copper sulfate solution with a copper cathode, the zinc rod loses weight as it oxidizes while copper precipitates and the solution warms due to heat released, demonstrating the spontaneous conversion of chemical to electrical energy in a galvanic cell.

1. Electrochemistry
( Galvanic cell )
Std 12 sci ( E )
Chapter-3 – Electrochemistry
Lecture – 2
By :- Ms. MAYRI R SOMPURA
HJD INSTITUTE KERA-
KUTCH

2. Electrochemistry
CATHODE – WHERE REDUCTION OCCURS
ANODE – WHERE OXIDATION OCCURS

3. GALVANIC CELL
CHEMICAL ENERGY ELECTRICAL ENERGY GALVANIC CELL
INPUT OUTPUT
 SPONTANEOUS Redox reaction occurs.
 Change in ΔG = + ve Non spontaneous
rxn = ΔG = +ve
Spontaneous = ΔG
= - ve
NOTE

5. OBSERVATION
• Weight of zinc rod decreases.
• Blue colour of solution disappears.
• Reddish brown ppts observed
• Temperature of copper sulphate
solution increases.
• Heat that is evolved can be used for generating
electrical energy.
CONCLUSION

6. GALVANIC CELL
LOAN – Galvanic cell
L – LEFT
O - OXIDATION
A - ANODE
N - NEGETIVE

7. COMPARISON
ELECTROLYTIC CELL
• Electrical energy → chemical
energy
• Non spontaneous redox reaction
• ΔG = +ve
• Anode → +ve
• Cathode → - ve
GALVANIC CELL
• Chemical energy → electrical
energy
• spontaneous redox reaction
• ΔG = - ve
• Anode → -ve
• Cathode → + ve

10. Salt bridge :-
• Salt bridge is an inverted U tube in which inert electrolyte is placed with
agar agar paste in a semi liquid state ( gel form ).
• Eg;
inert electrolytes such as KCl, KNO3, NaNO3, NH4NO2, NH4Cl
Working of a salt bridge :-
• It completes the circuit & maintains the flow of electrons.
• It maintains electrical neutrality of electrolyte solution.
• It also reduces junction-junction potential barrier.

12. Properties of electrolyte filled in U tube :-
1. They are usally inert & don’t react with the solution in half cell.
• Zn+2 + 2 Cl- → ZnCl2 ( highly soluble )
• But when we use silver electrode, we cannot use KCl
• Ag+ + Cl- → AgCl
2. Mobility ( speed ) of +ve & -ve ions of electrolyte filled in inverted U tube
must be same.
• Mobility of H+ / OH- is fastest.