Galvanic Cell
What is a galvanic cell?
A galvanic cell is an electrochemical cell that
converts the chemical energy of spontaneous redox
reactions into electrical energy.
The Anode is the negative or reducing electrode that releases
electrons to the external circuit and oxidizes(loses electrons)
during an electrochemical reaction.
The Cathode is the positive or oxidizing electrode that
acquires electrons from the external circuit and is reduced
(gains electrons) during the electrochemical reaction.
Electrolyte:
An aqueous substance that conducts electricity.
All solutions in a galvanic cell are electrolytes,
including the solutions in which the electrodes are
immersed and the solution that forms the salt bridge.
Construction of Galvanic Cell:
• The galvanic cell consists of two half cells:
• In the first compartment Zn plate is dipped inside
solution of zinc sulfate.
• In the second compartment Cu plate is dipped
inside solution of Copper (II) sulfate.
• The two plate are connected by connecting wires
and lamp or multimeter, while the two solutions are
connected by a salt bridge.
Interpretation:
• The Zn plate becomes thinner, while Cu plate
thicker in size (brown orange deposit Cu(S)).
• The color of copper (II) sulfate solution becomes
fade, thus the quantity of Cu2+ decreases in the
second compartment.
• Quantity of Zn2+ increases in the first compartment.
At the anode half cell ,if initial mass of anode was 3g,
its mass becomes 2g.
• Half reactions occurring:
• Anode half reaction: Zn → Zn2+ + 2e• Cathode half reaction: Cu2+ + 2e-→ Cu
• Over all reaction : Zn + Cu2+→ Zn2+ + Cu ; during
electrochemical reactions: nb of electrons lost = nb of
electrons gained.
• Cell Notation: Zn | Zn2+ - salt bridge-Cu2+|Cu
• Electrons flow from anode compartment (Zn) toward
cathode compartment (Cu).
• The anions in the salt brigde moves toward anode
compartment to neutralize the excess of Zn2+ ions, while
the cations move toward the cathode compartment to
neutralize the excess of negative ions in the solution.
Role of salt bridge:
• Completes the circuit.
• Prevent the mixing of two solutions.
• Allows ions to move through it, to keep electrical
neutrality of both compartments.
Clues
Anode
Cathode
Mass change{increase or
decrease}
decrease
Increase
Concentration (quantity) of
ions (increase or decrease)
increase
Decrease
Activity (more redundant or
less reductant)
More reductant
Less reductant
Polatiry (positive or
negative)
Negative
Positive
Type of reaction (oxidation
or reduction )
Oxidation
Reduction
Flow of electrons (From?
To?)
From
to
Flow of current (From ? To?)
to
from
Negative ions flow to anode
Positive ions flow to cathode
Flow of ions in the salt
bridge