Oxidation-reduction reactions

The word "oxidation" initially meant the interaction of a particular substance with oxygen, with the formation of an oxide, since oxygen was historically recognized as the first oxidant. Oxidation was understood as the addition of oxygen, and under restoration, it was the return of oxygen. So the term "oxidation-reduction" long ago operated chemistry. Oxidation-reduction reactions later began to be considered as such processes, as a result of which there is a transfer of electrons from one to another atom, so this term has acquired a wider meaning. For example, when magnesium burns in oxygen: 2Mg + O2 → 2MgO, electrons transfer from magnesium to oxygen.

Oxidation-reduction reactions are characterized by the fact that reactants, called oxidants and reducing agents, react in them. Substances whose atoms give up electrons are considered to be reducing agents. Chemical compounds, whose atoms take electrons, are called oxidants. In the above reaction, magnesium is a reducing agent, while itself oxidizes, that is, gives an electron. Oxygen is restored - takes an electron and is an oxidizing agent. Another example: CuO + H2 → Cu + H2O. When copper oxide is heated in a hydrogen current, copper ions receive electrons from hydrogen. Being an oxidizer, they are reduced to elemental copper. Hydrogen atoms give off electrons, being a reducing agent, and hydrogen itself is oxidized.

Thus, the oxidation and reduction processes occur simultaneously: the reducing agents are oxidized, and the oxidants are reduced. Oxidation-reduction reactions have received such a name, since there is an inextricable link between these reciprocal processes. That is, if there are atoms that give up electrons, then surely there are those that these electrons take. In this case, both the oxidant and the reducing agent change the degree of oxidation. As a result, chemical compounds can be formed with any type of bonding of atoms in molecules.

The main types of oxidation-reduction reactions are:

1. Intermolecular - oxidizing and reducing atoms are included in the composition of molecules of different chemical substances, for example: 2HCl + Zn → ZnCl2 + H2 ↑ (zinc - reducing agent, hydrogen cation - oxidizer).
2. Intramolecular - oxidizing and reducing atoms are part of the molecule of the same chemical substance, for example: KClO3 → 2KCl + 3O2 ↑ (in the molecule of the bertholets salt oxygen-reducer, chlorine-oxidizer).
3. Self-oxidation-self-reduction or disproportionation-the same chemical element in the reaction is both a reducing agent and an oxidizing agent, for example: 3HNO2 → HNO3 + 2NO ↑ + H2O (the nitrogen atom in nitrous acid is both a reducing agent and an oxidizer, the oxidation product is nitrogen Acid, the product of reduction - nitrogen monoxide).
4. Conformation or reproportionation is the same chemical element that has different degrees of oxidation in the molecule, resulting in a single oxidation state, for example: NH4NO3 → N2O + 2H2O.

Oxidation-reduction reactions can be presented in a general or electronic form. We can consider the example of the chemical interaction: 2FeCl3 + H2S → FeCl2 + S + 2HCl. Here, the iron atom is an oxidizer, since it takes one electron and changes the oxidation state from +3 to +2: Fe + ³ + e → Fe + ². The sulfur ion is a reducing agent, being oxidized, it gives an electron and changes the oxidation state from -2 to 0: Sˉ² - e → S °. Electronic or ion-electronic balance methods are used to arrange the stoichiometric coefficients in the equation.

Oxidation-reduction reactions are widespread and are of great importance, since they underlie the processes of combustion, decay, decay, respiration, metabolism, carbon dioxide assimilation by plants, and also at the basis of other biological processes. They are also used in various industries to produce metals and non-metals from their compounds. For example, they are based on the production of ammonia, sulfuric and nitric acids, some building materials, medicines and many other important products. They are also used in analytical chemistry to determine various chemical compounds.