(1
Give one methode of preparation and one importants use of each of Cr2O3 and KMnO4 .
Answers
What is Potassium Permanganate?
Potassium Permanganate (KMnO4) is an inorganic chemical compound. It is also known as Condy’s crystals or permanganate of potash.
A German-Dutch chemist Johann Rudolf Glauber was the first to discover the production of KMnO4 in the year 1659. This compound is water-soluble and consists of two ions: Permanganate ion and potassium ion. It is a dark purple odourless solid in its physical state.
When potassium permanganate crystals are dissolved in water the solution formed is purple. It is considered as a strong oxidizing agent and does not produce toxic by products. It is usually prepared from other minerals such as manganese oxide
Structure of Potassium Permanganate (KMnO4)
The structure of potassium permanganate molecules is illustrated below. Note that this compound features an ionic bond between the potassium cation and the permanganate anion.
Reactions Of Potassium Permanganate (KMnO4)
1. Thermal decomposition:
When solid potassium permanganate is heated it undergoes decomposition. The reaction is as follows:
2KMnO4 → K2MnO4 + MnO2(s) + O2
2. Reaction with acid:
When permanganate reacts with concentrated hydrochloric acid it produces chlorine. In a neutral solution, permanganate is reduced by three electrons to produce manganese dioxide, where the oxidation state of manganese is +4. Potassium permanganate reduces spontaneously in an alkaline solution and turns into green K2MnO4.
3. Effect of Alkalies
On heating with alkalies, potassium permanganate changes into manganate and oxygen gas is evolved.
4KMnO4 + 4KOH → 4K2MnO4 + 2H2O + O2
4. Oxidizing properties
KMnO4 acts as a very powerful oxidizing agent in acidic, neutral and alkaline media. The equations representing oxidation in these media are
In acidic medium
2KMnO4 + H2SO4 → K2SO4 + 2MnSO4 + 3H2O + 5[O] MnO4– + 8H+ + 5e– → Mn2+ + 4H2O
In neutral or alkaline medium
2KMnO4 + H2O → 2KOH + 2MnO2 + 3[O] MnO4– + 2H2O + 3e– → MnO2 + 4OH–
Uses Of Potassium Permanganate (KMnO4)
There are wide applications of KMnO4. Some important uses of potassium permanganate have been discussed below:
Potassium permanganate is used in qualitative analysis to determine the permanganate value
KMnO4 is also used as a regeneration chemical in well water treatment for the removal of hydrogen sulphide and iron
This compound is also used as a disinfectant to cure certain skin conditions like foot fungal infections, dermatitis
Another important application of potassium permanganate is in the treatment of bacterial infections
KMnO4 is also known to be used in tanning leathers, printing fabrics
This compound can even be used as a bleaching agent, as a pesticide, and as an antiseptic
One of the most important industrial applications of potassium permanganate is as an oxidizing agent in the chemical synthesis of many important compounds.