In chemistry, the term electrolyte refers generically to substances that in solution or in the molten state undergo subdivision into ions of their molecules. Substances that do not dissociate are called non-electrolytes.
The term "electrolyte" refers to the ability to conduct electricity through the intervention of ions, a peculiar characteristic of these chemical species. Therefore, an electrolyte constitutes what is called an ionic conductor or, alternatively, a conductor of a second species. Electrolytes are capable of conducting the electric current, once dissolved in solution, precisely because of the presence of positive and negative ions generated in the solution, derived from the dissociation and ionization of the electrolyte.
The conduction is not linked, in this case, to the free flow of electrons inside a crystalline structure, but it is the ions that are in charge of "charging" the electric current. Defines an ampholyte an electrolyte with an amphoteric behavior. The salient properties of electrolytes are the ionic conductivity, the colligative properties and the pH of the solutions to which they give rise.
An electrochemical cell can contain two different electrolytes electrically connected by a salt bridge or a porous partition; in this case, the electrolyte in contact with the cathode is called catholyte, while the electrolyte in contact with the anode is called anolyte.
Examples of electrolytes
Regarding the chemical nature, acids, bases and salts are electrolytes. From the point of view of the state of aggregation, the electrolytes can be subdivided into:
- electrolytic solutions (for example, hydrochloric acid and sulfuric acid);
- solid electrolytes (eg, & beta; - alumina, allotropic form of aluminum oxide);
- ionic solids (eg, sodium chloride, silver iodide and calcium fluoride);
- molten salts (eg alkali nitrates).
Strong and weak electrolytes
With reference to a solution, a strong electrolyte is present in a single liquid phase in the solvated ion state.
A weak electrolyte is an electrolyte that dissociates in water only partially. A weak electrolyte has a chemical equilibrium between the undissociated molecular form and the ions that derive from it by dissociation. The dissociation increases if the solution is diluted. The degree of dissociation is a parameter that identifies the quantitative level of ionic dissociation.
Electrolytes are essential components of electrochemical cells (including galvanic cells and electrolyte cells), where they have the function of transporting the electrical charge from one electrode to another. In an electrochemical cell, two electrolyte solutions may also be present, separated by a porous septum or by a salt bridge.
Electrolytes are used inside particular capacitors, called electrolytic capacitors.
Electrolytes can also be used to perform the operations of the flocculation unit (used in wastewater treatment) and ion exchange (used in water softening and in ion exchange chromatography operations).
Electrolytes are essential for some biological processes, such as the sodium and potassium pump. In the blood, and specifically in the plasma, sodium, potassium, phosphate, magnesium, iron, calcium and others are present. In diagnostic medicine, the parameters are measured in blood tests with various technologies, including the membrane electrode.