The electronic exchange that occurs in an oxidation-reduction reaction is used to establish devices that convert the energy released in a REDOX process into electrical energy. These devices are called galvanic cells or electrochemical cells. A battery is established when the oxidation and reduction processes occur in separate compartments, linked only by a conducting wire (metal).
Reaction under study:
Components of a galvanic cell
- Cell where the oxidation half-reaction occurs.
- Cell where the reduction half-reaction occurs.
- Salt bridge (equalizes the electrical charges in both cells).
- Metal electrodes (devices where electrons are transferred).
- Ionic solutions (medium in which the transfer occurs).
- Voltmeter, electronic device that verifies the passage of electrons in the conductive wire.
Operation of a galvanic battery
When connecting the metallic plates with the conductive wire, the spontaneous flow of electrons occurs, evidenced by a light bulb that lights up or a voltmeter that measures the potential difference of the battery (difference between the electrodes).
Over time it is observed that the copper (Cu) plate increases in mass, while the zinc (Zn) plate dissolves (loses mass). This difference in the masses of the plates is justified by the progress of the oxidation-reduction reaction (passage of electrons).
To avoid the accumulation of charges in the vicinity of the plates, a salt bridge (electroneutrality) is placed between the compartments.
On the metal plates (electrodes), the following occurs respectively:
Cathode: reduction reaction
Anode: oxidation reaction
Notation of a galvanic cell
The notation of a battery involves describing it according to the reactions that occur in each cell, with the understanding that reduction will always occur at the cathode and oxidation at the anode. The writing is made from right to left considering as first reaction the oxidation and indicating separately the initial species from the oxidized one by a slash, then a double slash separates one cell from the other and continues with the cathode reaction, as illustrated in the figure of the battery previously studied.
