Potassium Permanganate Formula Structure, Properties, Uses, Sample Questions (original) (raw)

Last Updated : 20 Dec, 2023

Potassium (K) is a chemical element and its atomic number is 19 in the periodic table. Potassium is a silvery-white metal that is soft enough to be cut with a knife by a little bit of force. It reacts with oxygen to form flaky white potassium peroxide. Permanganate is a chemical compound containing the manganate(VII) ion, MnO⁻₄, the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent.

Potassium Permanganate

Potassium Permanganate is an inorganic chemical compound. This compound consists of two ions, Permanganate ion (MnO-4) and potassium ion (K+). It is a dark purple odorless solid. When potassium permanganate is dissolved in water the solution formed is purple in color. It is known as a strong oxidizing agent and does not produce toxic products. It is prepared from other minerals such as manganese oxide.

**Formula of Potassium Permanganate

The chemical formula of Potassium Permanganate is KMnO-4.

**Structure of Potassium Permanganate

There exists this ionic bond between the potassium cation and the permanganate anion.

**Preparation of Potassium Permanganate

• Potassium permanganate is prepared by mixing a solution of KOH and powdered manganese oxide, with oxidizing agents like potassium chlorate. This mixture is boiled and evaporated, and the residue is heated in iron pans until it has acquired a pasty consistency.

6KOH + 3MnO2 + 6KClO3 → 3K2MnO4 + 6KCl + 3H2O

The potassium manganate (K2MnO4) that is formed is then boiled with water and chlorine and ozonized air is passed into the liquid until it is converted into permanganate.

6K2MnO4 + 3Cl2 → 6KMnO4 + 6KCl.

**Physical Properties Of Potassium Permanganate

• The Molecular weight of Potassium permanganate is 158.034 g/mol.
• The Density of Potassium permanganate is 2.703 g/cm³.
• The Boiling Point of Potassium permanganate is 100°C.
• The Melting Point of Potassium permanganate is 240°C.
• The Oxidation State of Potassium Permanganate is +7.
• It is an odorless purple crystalline solid.
• It is soluble in water and more soluble in boiling water. It can dissolve in acetone, acetic acid, methanol, pyridine, ethanol, and organic compounds.
• This compound has a slightly acid or bitter taste.

**Chemical Properties Of Potassium Permanganate

• **Thermal decomposition: Potassium permanganate undergoes thermal decomposition when it is heated.

2KMnO4 → K2MnO4 + MnO2 + O2.

• **Potassium Permanganate Reacted with acid: When permanganate reacts with concentrated hydrochloric acid it produces chlorine. Potassium permanganate reduces to an alkaline solution and turns into green K2MnO4.

2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 5H2O + 8Cl2.

• **Effect of Alkalies: When Potassium permanganate is heated with alkalies, it changes into manganate, and oxygen gas is evolved.

4KMnO4 + 4KOH → 4K2MnO4 + 2H2O + O2

• **Oxidizing properties: KMnO4 acts as a very powerful oxidizing agent in acidic, neutral, and alkaline media. The following are the equations in oxidation.

**In acidic medium

2KMnO4 + H2SO4 → K2SO4+ 2MnSO4 + 3H2O + 5[O]

MnO-4+ 8H+ + 5e- → Mn2 + + 4H2O

**In neutral or alkaline medium

2KMnO4 + H2O → 2KOH + 2MnO2 + 3[O]

MnO-4 + 2H2O + 3e- → MnO2 + 4OH-

**Uses Of Potassium Permanganate

• It is used to determine the permanganate value. It is used as an in-well water treatment for the removal of hydrogen sulfide and iron.
• It is used as a disinfectant to cure certain skin conditions like fungal infections, and dermatitis.
• It can be in the treatment of bacterial infections.
• It is used in industries like leather tanning, and fabrics printing.

Sample Questions

**Question 1: Why is Potassium Permanganate known as a good oxidizing agent?

**Answer:

Potassium Permanganate is known as oxidizing agent as the oxidation states of atoms increase the elements become more electronegative. It can be used as an oxidizing agent in the chemical synthesis of many important compounds.

**Question 2: What is the color of potassium permanganate?

**Answer:

Potassium permanganate in its physical state, it is an odourless solid, and it look like crystals of dark purple colour. When it is dissolved in water, the solution becomes purple in colour.

**Question 3: Why KMnO 4 is a self indicator?

**Answer:

Permanganate ions losses it's pink colour when they are used up in the reaction. It recommends the end of the reaction and therefore it is called as a self-indicator, as potassium permanganate serves as an indicator apart from being one of the reactants.

**Question 4: What happens when potassium permanganate reacts with CO 2 ?

**Answer:

Potassium manganate turns purple when CO2 gas is passed through the solution.CO2 reacts with water to form carbonic acid as given below:

CO2 + H2O ⇌ H2CO3

**Question 5: What are the effects of using Potassium Permanganate?

**Answer:

It can irritate human eyes and skin. . When used it leaves a stain on skin or tissues. Potassium permanganate should be handled with care, it may occur explosion when it comes in contact with readily oxidizable substances.

**Question 6: An acidified solution of potassium permanganate oxidizes?

**Answer:

Reaction of permanganate solution with sulphurous acid.

2MnO-4 + 5SO2-3 + 6H+ → 5SO2-4 + 2Mn+2 + 3H2O

Thus, oxidises sulphites.

**Question 7: What are pH values, when a solution of KMnO 4 is reduced to various products.

**Answer:

• At pH < 7 it is reduced to a colourless solution Mn2+
• At pH = 7 it forms a brown precipitate MnO2.
• At pH > 7 it gives a green solution MnO2-4.