The word "oxidation" originally meantthe 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" has long operated on chemistry. Oxidation-reduction reactions later became regarded as such processes, as a result of which the transfer of electrons from one to another atom occurs, 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 reactionscharacterized by the fact that they reacted with reagents, called oxidants and reducing agents. Substances whose atoms give up electrons are considered reducing agents. Chemical compounds, the atoms of which take electrons, are called oxidants. In the above reaction, magnesium is a reducing agent, while itself is oxidized, 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 hydrogen from hydrogen. As an oxidizer, they are reduced to elemental copper. Hydrogen atoms give off electrons, being a reducing agent, and hydrogen itself is oxidized.
Thus, the processes of oxidation andRecovery occurs simultaneously: reducing agents are oxidized, and 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:
- 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).
- Intramolecular - oxidizing andthe 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).
- Self-oxidation-self-repair ordisproportionation - 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 nitric acid, the product of reduction - nitrogen monoxide).
- Conformation or Reproportionation -the same chemical element having different degrees of oxidation in the molecule results in a single oxidation state, for example: NH4NO3 → N2O + 2H2O.
Oxidation-reduction reactions occurare presented in 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, oxidizing, 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 widelyare 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.