Electrical dissociation: the theoretical foundations of electrochemistry

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Electrical dissociation plays a huge role in our lives, although we usually do not think about it. It is with this phenomenon that the electrical conductivity of s alts, acids and bases in a liquid medium is associated. From the first heartbeats caused by “living” electricity in the human body, which is eighty percent liquid, to cars, mobile phones and players, the batteries of which are essentially electrochemical batteries, electrical dissociation is invisibly present everywhere near us.

In gigantic vats emitting toxic fumes from bauxite melted at high temperatures, the "winged" metal - aluminum is obtained by electrolysis. Everything around us, from chrome radiator grilles to silver-plated earrings in our ears, onceor faced with solutions or molten s alts, and hence with this phenomenon. No wonder electrical dissociation is studied by a whole branch of science - electrochemistry.

When dissolved, the molecules of the solvent liquid enter into a chemical bond with the molecules of the dissolved substance, forming solvates. In an aqueous solution, s alts, acids and bases are most susceptible to dissociation. As a result of this process, the solute molecules can decompose into ions. For example, under the influence of an aqueous solvent, the Na⁺ and CI^{- ions in the NaCl ionic crystal pass into the solvent medium in a new quality of solvated (hydrated) particles.}

This phenomenon, which is essentially the process of complete or partial decomposition of a dissolved substance into ions as a result of the action of a solvent, is called "electric dissociation". This process is extremely important for electrochemistry. Of great importance is the fact that the dissociation of complex multicomponent systems is characterized by a stepwise flow. With this phenomenon, there is also a sharp increase in the number of ions in solution, which distinguishes electrolytic substances from non-electrolytic ones.

In the process of electrolysis, ions have a clear direction of movement: particles with a positive charge (cations) - to a negatively charged electrode, called the cathode, and positive ions (anions) - to the anode, an electrode with the opposite charge, where they are discharged. Cations are reduced and anions are oxidized. Therefore, dissociation is a reversible process.

One of the fundamental characteristics of this electrochemical process is the degree of electrolytic dissociation, which is expressed as the ratio of the number of hydrated particles to the total number of molecules of the dissolved substance. The higher this indicator, the stronger the electrolyte is this substance. On this basis, all substances are divided into weak, medium strength and strong electrolytes.

The degree of dissociation depends on the following factors: a) the nature of the solute; b) the nature of the solvent, its dielectric constant and polarity; c) concentration of the solution (the lower this indicator, the greater the degree of dissociation); d) the temperature of the dissolving medium. For example, the dissociation of acetic acid can be expressed by the following formula:

CH₃COOH H⁺ + CH₃COO^-

Strong electrolytes dissociate almost irreversibly, since their aqueous solution does not contain the original molecules and non-hydrated ions. It should also be added that all substances that have an ionic and covalent polar type of chemical bonds are subject to the dissociation process. The theory of electrolytic dissociation was formulated by the outstanding Swedish physicist and chemist Svante Arrhenius in 1887.