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An oxidizing agent (also known as an oxidizer or an oxidant) is a chemical species that tend to oxidize other substances, causing the oxidation state of the material to rise by causing it to lose electrons. Halogens (such as chlorine and fluorine), oxygen, and hydrogen peroxide are examples of oxidizing agents.
Because oxidizing agents are generally found at their maximum potential oxidation states, they have a strong proclivity to acquire electrons and undergo reduction. Ions, atoms, and molecules with a high affinity for electrons are regarded as excellent oxidizers. The higher the electron affinity, the more powerful the oxidizing power.
Potassium permanganate and potassium dichromate are two strong oxidizing agents.
Potassium permanganate, commonly known as potash permanganate, has the chemical formula KMnO4. It’s made from the mineral pyrolusite. Potassium Permanganate is an odourless solid that resembles dark purple or bronze-coloured crystals. K2Cr2O7 is the chemical formula for potassium dichromate. Chromite ore is used to make K2Cr2O7. It is a crystalline substance that is red-orange in colour.
The following stages are involved in the preparation of KMnO4:
2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O
Chemical oxidation: Potassium permanganate is formed by treating potassium manganate with chlorine or ozone.
2K2MnO4 + Cl2 →2KMnO4 +2KCl
2K2MnO4 + H2O+O3 →2KMnO4 +2KOH+O2
Electrolytic oxidation: The potassium manganate solution is electrolyzed in this manner.
K2MnO4 ⇔2K++MNO2-4
H2O⇔H++OH–
MnO42-→MnO4–+e–
The green colour solution transforms to a purple colour solution after oxidation, which is concentrated by evaporation and forms crystals upon cooling.
Potassium permanganate is an ionic compound made up of a potassium cation (K+) and the permanganate anion (MnO4–). The manganese atom in the permanganate anion is connected to four oxygen atoms through three double bonds and one single bond. Manganese’s oxidation state in this salt is +7. Solid KMnO4 has an orthorhombic crystal structure. Each (MnO4–) structure has a tetrahedral geometry.
2KMnO4→ K2MnO4 +MnO2+ O2
Preparation
Potassium dichromate is a widely used chemical in the industry as an oxidising agent and in the synthesis of a variety of other chemicals.
Dichromates are often made from chromates, which are made by combining chromite ore with sodium/potassium carbonate in the presence of air.
4FeCr2O4 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2
2Na2CrO4 + 2H+ → Na2Cr2O7 + 2Na+ + H2O
Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl
As a result, we eventually have orange crystals of potassium dichromate.
The chromate ion has a tetrahedral shape, but the dichromate ion is made up of two tetrahedra that share one corner and have a bond angle of 126° with the chromate ion. Potassium dichromate’s chemical/molecular formula is K2Cr2O7, and its molecular mass is 294.185 g/mol. Potassium dichromate is an ionic compound composed of two potassium ions and one negatively charged dichromate ion.
In dichromate ion, two hexagonal chromium ions have an oxidation state of +6 and are bound to three oxygen atoms each as well as a bridging oxygen atom.
4K2Cr2O7 + 2CrO3 + 3O2 →4K2CrO4+ 2CrO3 + 3O2
Potassium dichromate is a gentler oxidizing agent than potassium permanganate in organic chemistry. It is employed in the oxidation of alcohol. Under more severe circumstances, this transforms primary alcohols into aldehydes and carboxylic acids.
As a result, after all of the permanganate ions are used in the reaction, the solution loses its pink colour. It denotes the conclusion of the reaction, and so potassium permanganate is known as a self-indicator since it works as an indicator in addition to being one of the reactants.
Because the concentrated solutions and crystals of potassium permanganate are caustic in nature, they can cause skin irritation. Even if the solution is diluted, it can cause irritation, and repeated application of the potassium permanganate solution to the skin can result in severe skin burn.