word "oxidation" initially involves the specific interaction of a substance with oxygen to form an oxide, as oxygen has historically been recognized as the first oxidant.By joining oxygen oxidation understood, and under restoration - out of it.So the term "oxidation - restoration" has long operated chemistry.Redox reactions later came to be considered such processes that result in the transfer of electrons from one atom to another, so this term has a broader meaning.For example, when magnesium combustion in oxygen: 2Mg + O2 → 2MgO occurs transfer of electrons from magnesium to oxygen.
Redox reactions are characterized by the fact that they interact with the reagents, called oxidants and reducing agents.Substances whose atoms donate electrons, reducing considered.Chemicals, which accept electrons atoms called oxidants.In the above reaction, magnesium is a reducing agent itself is oxidized, i.e. donates an electron.Oxygen is restored - takes an electron and an oxidizer.Another example: CuO + H2 → Cu + H2O.When copper oxide is heated in a hydrogen stream copper ions accept electrons from hydrogen.As an oxidizer, they are reduced to elemental copper.Hydrogen atoms donate electrons, as a reducing agent, and the hydrogen is oxidized.
Thus, the oxidation and reduction processes take place simultaneously: reducing oxidized and oxidizing agents are reduced.Redox reactions are so called as between the reciprocal processes are inextricably linked.That is, if there are atoms that donate electrons, make sure there are those who are taking these electrons.Here as in the oxidant and reductant in the oxidation state varies.As a result of chemical compounds can be formed with any type of atoms in molecules.
main types of redox reactions:
- Intermolecular - oxidizing and restores the atoms are part of the molecules of different chemicals, such as: 2HCl + Zn → ZnCl2 + H2 ↑ (zinc - reducing agent, hydrogen cation - oxidant).
- intramolecular - oxidizing and restores the atoms are part of the molecules of the same chemical substance, such as: KClO3 → 2KCl + 3O2 ↑ (in the molecule of potassium chlorate oxygen - reducing agent, chlorine - oxidant).
- autoxidation-self-healing or disproportionation - the same chemical element in the reaction is the reducing agent and oxidizing agent, for example: 3HNO2 → HNO3 + 2NO ↑ + H2O (nitrogen in nitric acid is both a reducing agent and oxidizing agent, the oxidation product -is nitric acid, the reduction product - nitrogen monoxide).
- Comproportionation or reproportsionirovanie - the same chemical element present in the molecule, varying degrees of oxidation, resulting in a single oxidation state, for example: NH4NO3 → N2O + 2H2O.
Redox reactions are presented in a general form or electronically.You can see an example of chemical interaction: 2FeCl3 + H2S → FeCl2 + S + 2HCl.Here, the iron atom is an oxidizing agent, because it takes an electron and change the oxidation state from +3 at +2: Fe + ³ + e → Fe + ².Ion reducing sulfur is oxidized, it gives up an electron and change the oxidation state of -2 to 0: Sˉ² - e → S °.Methods of electron-electron or ion balance are used for placement of stoichiometric coefficients in the equation.
Redox reactions are common and are important because they underpin the processes of combustion, rotting, decay, respiration, metabolism, assimilation of carbon dioxide by plants, as well as through other biological processes.They also are used in various industries for the production of metals and non-metals from their compounds.For example, these are based on ammonia, sulfuric and nitric acids, some building materials, medicines and many other important products.They are also used in analytical chemistry for determining the various chemical compounds.
