Galvanic Cells Overview

Study Notes

Galvanic cells convert chemical energy from spontaneous redox reactions into electrical energy.
Gibbs energy from the redox reaction is transformed into electrical work for powering devices like motors or heaters.

A primary example of a galvanic cell is the Daniell cell, which operates on the reaction:
- Zn(s) + Cu2+(aq) -> Zn2+(aq) + Cu(s)
The overall cell reaction comprises two half-reactions:
- Reduction: Cu2+ + 2e- -> Cu(s)
- Oxidation: Zn(s) -> Zn2+ + 2e-

The two half-reactions occur in separate parts of the cell known as half-cells or redox couples.
The copper electrode is designated as the reduction half-cell, while the zinc electrode is termed the oxidation half-cell.
Each half-cell consists of a metallic electrode submerged in an electrolyte solution.

Half-cells are connected externally by a metallic wire, a voltmeter, and a switch.
Internally, the half-cells connect via a salt bridge, facilitating ionic movement.

At the electrode-electrolyte interface, ions from the solution can deposit on the electrode, causing a positive charge.
Conversely, metal atoms from the electrode may enter the solution as ions, leading to a negative charge at the electrode.
This charge separation results in an electrode potential, which is the potential difference between the electrode and the electrolyte.
When all species in a half-cell reach unity concentration, the electrode potential is termed standard electrode potential.

The half-cell where oxidation occurs is known as the anode, exhibiting a negative potential relative to the solution.
Conversely, the half-cell where reduction occurs is the cathode, having a positive potential relative to the solution.
A potential difference induces the flow of electrons from the anode (negative electrode) to the cathode (positive electrode).
The flow of current, however, moves in the opposite direction to electron flow, following conventional current direction.