ELECTRO CHEMISTRY l GALVANIC CELL l SCIENCE OF BATTERIES l DANIEL CELL l CHEMISTRY OF DANIEL 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.