Redox processes underlie the most important phenomena of animate and inanimate nature: combustion, decomposition of complex substances, synthesis of organic compounds. Potassium permanganate, the properties of which we will study in our article, is one of the most powerful oxidizing agents used in laboratory and industrial conditions. Its oxidizing abilities depend on the degree of oxidation of the atom, which changes during the reaction. Let us consider this with specific examples of chemical processes involving KMnO 4 molecules.
Substance characteristics
The compound under consideration (potassium permanganate) is one of the most used substances in the industry - manganese compounds. Salt is represented by crystals in the form of regular prisms of dark purple color. It is well soluble in water and forms a raspberry-colored solution with excellent bactericidal characteristics. Therefore, the substance has been widely used both in medicine and in everyday life as a bactericidal agent. Like other compounds of heptavalent manganese, the salt is able to oxidize many compounds of an organic and inorganic nature. The decomposition of potassium permanganate is used in chemical laboratories to obtain small volumes of pure oxygen. The compound oxidizes sulfite acid to sulfate. In industry, KMnO 4 is used to separate chlorine gas from hydrochloric acid. It also oxidizes most organic substances, is capable of converting ferrous salts into the form of its ferric compounds.
Experiments with potassium permanganate
A substance in the home called potassium permanganate decomposes when heated. Free oxygen, manganese dioxide and a new salt, K 2 MnO 4, are found in the reaction products. In the laboratory, this process is carried out to obtain pure oxygen. The chemical equation for the decomposition of potassium permanganate can be represented as follows:
2KMnO 4 = K 2 MnO 4 + MnO 2 + O 2 .
The dry substance, which is purple crystals in the form of regular prisms, is heated to a temperature of +200 ° C. The manganese cation in the salt has an oxidation state of +7. It decreases in the reaction products to values of +6 and +4, respectively.
Ethylene Oxidation
Gaseous hydrocarbons belonging to different classes of organic compounds have both single and multiple bonds between carbon atoms in the composition of their molecules. How to determine the presence of pi bonds underlying the unsaturated nature of the organic compound? To do this, conduct chemical experiments by passing the test substance (for example, ethene or acetylene) through a violet solution of potassium permanganate. Its discoloration is observed, since the unsaturated bond is destroyed. The ethylene molecule is oxidized and turns from a unsaturated hydrocarbon into a diatomic saturated alcohol - ethylene glycol. This reaction is qualitative for the presence of double or triple bonds.
Features of chemical manifestations of KMnO4
If the oxidation states of the reactants and reaction products change, then the oxidation-reduction reaction occurs. It is based on the phenomenon of the movement of electrons from one atom to another. As in the case of the decomposition of potassium permanganate, as in other reactions, the substance exhibits pronounced oxidizing properties. For example, in an acidified solution of sodium sulfite and potassium permanganate, sodium, potassium and manganese sulfates are formed, as well as water:
5Na 2 SO 3 + 2KMnO 4 + 3H 2 SO 4 = 2MnSO 4 + 5Na 2 SO 4 + K 2 SO 4 + 3H 2 0.
In this case, the sulfur ion is a reducing agent, and manganese, which is part of the complex anion MnO 4 - , exhibits the properties of an oxidizing agent. It takes five electrons, so the degree of oxidation decreases from +7 to +2.
The influence of the medium on the course of a chemical reaction
Depending on the concentration of hydrogen ions or hydroxyl groups, the acidic, alkaline or neutral nature of the solution in which the redox reaction occurs is distinguished. For example, with an excessive content of hydrogen cations, a manganese ion with an oxidation state of +7 in potassium permanganate lowers it to +2. In an alkaline environment, at a high concentration of hydroxyl groups, sodium sulfite, interacting with potassium permanganate, is oxidized to sulfate. A manganese ion with an oxidation state of +7 transforms into a cation with a charge of +6, which is part of K 2 MnO 4 , the solution of which has a green color. In a neutral environment, sodium sulfite and potassium permanganate react with each other, while manganese dioxide is precipitated. The oxidation state of the manganese cation decreases from +7 to +4. Sodium sulfate and alkali, sodium hydroxide, are also found in the reaction products.
The use of salts of manganese acid
The decomposition reaction of potassium permanganate upon heating and other redox processes involving manganese acid salts are often used in industry. For example, the oxidation of many organic compounds, the evolution of chlorine gas from hydrochloric acid, the conversion of ferrous salts to ferric. In agriculture, KMnO 4 solution is used for presowing treatment of seeds and soil, in medicine they treat the surface of wounds, disinfect inflamed mucous membranes of the nasal cavity, and use them for disinfecting personal hygiene items.
In our article, we not only studied in detail the process of decomposition of potassium permanganate, but also examined its oxidizing properties and applications in everyday life and industry.