Galvanic cell
A galvanic cell, also known as a voltaic cell, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. Here are the key points about galvanic cells:
- Basic Components:
- Two Electrodes: An anode (negative electrode) and a cathode (positive electrode).
- Electrolyte: A substance that contains free ions and can be a liquid, gel, or solid.
- External Circuit: Conductive wire or material connecting the two electrodes.
- Functioning:
- In a galvanic cell, a redox reaction is split into two half-reactions, with the oxidation reaction occurring at the anode and the reduction reaction at the cathode.
- Electrons flow through the external circuit from the anode to the cathode, providing electrical energy.
- Electrode Reactions:
- At the anode, oxidation (loss of electrons) occurs.
- At the cathode, reduction (gain of electrons) takes place.
- Salt Bridge:
- Often, a salt bridge or a porous membrane is used to maintain electrical neutrality by allowing ions to flow between the two half-cells.
- Spontaneity of Reactions:
- The reactions in a galvanic cell occur spontaneously, generating an electric current.
- Applications:
- Batteries are common examples of galvanic cells.
- Used in various applications where portable electrical energy is required.
- Voltage or Cell Potential:
- The voltage of a galvanic cell depends on the nature of the electrodes and the electrolyte, as well as the concentrations of reactants and products.
- Standard Electrode Potential:
- The standard electrode potential is measured under standard conditions (25°C, 1 M concentration, and 1 atm pressure) and is used to predict the direction of the reaction and the cell potential.
- Examples:
- A common example is the Daniell cell, which consists of a zinc electrode in a zinc sulfate solution and a copper electrode in a copper sulfate solution.
Galvanic cells are fundamental in the field of electrochemistry and are the basis for many types of batteries. They illustrate the direct conversion of chemical energy into electrical energy through electrochemical reactions.