Definition and Purpose
Electrochemical cells are devices that convert chemical energy into electrical energy (galvanic/voltaic cells) or use electrical energy to drive chemical changes (electrolytic cells). They rely on redox (reduction–oxidation) reactions, where electron transfer occurs between chemical species.
Types of Electrochemical Cells
- Galvanic (Voltaic) Cells
- Operate spontaneously to produce electrical energy.
- Used in batteries and fuel cells.
- Electrolytic Cells
- Require an external power source to drive non-spontaneous reactions.
- Used in electroplating, metal refining, and decomposition reactions.
Components of a Galvanic Cell
A typical galvanic cell consists of two half-cells, each containing an electrode and an electrolyte, a salt bridge or porous membrane to maintain charge balance and an external wire connecting the electrodes for electron flow.
Anode and Cathode
Anode: Site of oxidation (electrons are released).
Cathode: Site of reduction (electrons are gained).
Electrons flow from the anode to the cathode through the external circuit. In the salt bridge, ions migrate to balance charge buildup: anions move toward the anode, and cations toward the cathode.
Standard Cell Notation
Cell reactions can be represented using shorthand notation:
Anode | Anode solution || Cathode solution | Cathode
Example: Zn (s) | Zn\(^{2+}\)(aq) || Cu\(^{2+}\)(aq) | Cu (s)
Applications
Galvanic cells: commercial batteries (e.g., alkaline, lithium-ion).
Electrolytic cells: production of aluminum, electrolysis of water, electroplating.
Biological systems: electrochemical gradients in nerve function and energy storage (e.g., ATP synthesis).
Common Errors to Avoid
- Confusing the direction of electron flow.
- Reversing anode and cathode roles.
- Using incorrect standard potentials or misapplying signs.
- Ignoring stoichiometry in redox balancing.
Conclusion
Electrochemical cells are essential for understanding how chemical energy is harnessed and manipulated. A deep understanding of electrode potentials, redox behavior, and cell construction is critical for both theoretical knowledge and practical applications.
Written by Rand Ranj