electrolyte(redirected from electrolyte affinity)
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a liquid or solid compound or system in which some noticeable concentration of ions that provide for the passage of electric current is present. In the narrow sense, electrolytes are substances whose solutions conduct electric current by means of ions, formed as a result of electrolytic dissociation.
A distinction is made between strong and weak electrolytes in solution. Strong electrolytes virtually completely dissociate into ions in dilute solutions. They include many inorganic salts and several inorganic acids and bases in aqueous solutions and in solvents possessing high dissociating capacity, such as alcohols and amides. The molecules of weak electrolytes in solution are only partially dissociated into ions, which are in dynamic equilibrium with the undissociated molecules. Weak electrolytes include most organic acids and many organic bases in aqueous and nonaqueous solvents. The division of electrolytes into strong and weak electrolytes is somewhat arbitrary, since it reflects not the properties of the electrolytes themselves but their state in solution, which depends on the concentration, on the nature of the solvent, on temperature, and on pressure.
On the basis of the number of ions into which one electrolyte molecule dissociates in solution, a distinction is made between binary electrolytes (written 1–1 electrolytes; for example, KCl), unibivalent electrolytes (written 1–2 electrolytes; for example, CaCl2), and so forth. Electrolytes of types 1–1, 2–2, and 3–3 are called symmetrical electrolytes, while electrolytes of types 1–2 and 1–3 are called nonsymmetrical electrolytes.
The properties of dilute solutions of weak electrolytes are described satisfactorily by the classical theory of electrolytic dissociation. The theory is inapplicable for insufficiently dilute solutions of weak electrolytes and for solutions of strong electrolytes, since these are complex systems consisting of ions, undissociated molecules or ion pairs, and larger aggregates. The properties of such solutions are determined by the nature of the ion-ion and ion-solvent interactions and by changes in the properties and structure of the solvent caused by the dissolved particles. The modern statistical theories of strong electrolytes adequately describe the properties of only very dilute solutions (<0.1 mole/liter).
Electrolytes are extremely important in science and technology. All liquid systems in living organisms contain electrolytes. Polyelectrolytes constitute an important class of electrolytes (seePOLYELECTROLYTE). Electrolytes are a medium for carrying out many chemical syntheses and electrochemical production processes. Nonaqueous electrolyte solutions are playing an ever increasing role in these applications. The study of the properties of electrolyte solutions is important in the design of new chemical sources of electric current and the improvement of technological processes for the separation of compounds by extraction from solution and ion exchange.
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A. I. MISHUSTIN