Potassium permanganate

Potassium permanganate (KMnO₄) is a dark purple, crystalline chemical compound that is widely used for its oxidizing properties. It is water-soluble and forms a bright purple solution. It is a strong oxidizing agent in both acidic and neutral conditions.

Uses of Potassium Permanganate

Medical Uses:
- Antiseptic: Used to treat skin infections like athlete’s foot, eczema, and ulcers.
- Disinfectant: Employed in dilute solutions to cleanse wounds.
Water Treatment:
- Removes iron and manganese from water supplies.
- Acts as a disinfectant to kill bacteria and algae.
Chemical Reactions:
- Strong oxidizing agent in organic and inorganic synthesis.
- Used in qualitative analysis to test for the presence of unsaturated hydrocarbons and aldehydes.
Agriculture:
- Treats fungal infections in plants.
- Sterilizes seeds before sowing.
Industrial Applications:
- Bleaching agent in textiles and paper industries.
- Used in manufacturing chemicals like saccharin.
Environmental Applications:
- Detoxifies industrial waste.
- Removes hydrogen sulfide and organic contaminants from wastewater.
Household Uses:
- Purifies water in emergency situations.
- Disinfects aquariums and fish tanks.

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Preparation of Potassium Permanganate

Potassium permanganate is typically prepared by the oxidation of manganese compounds. A common method involves the following steps:

Conversion to Manganese Dioxide (MnO₂):

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Manganese ores (pyrolusite) are heated with potassium hydroxide (KOH) and oxygen or an oxidizing agent (like potassium nitrate, KNO₃) to form potassium manganate (K₂MnO₄).

2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O

Oxidation to Potassium Permanganate:

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Potassium manganate is disproportionated in acidic or neutral conditions to form potassium permanganate.

3K₂MnO₄ + 2H₂O → 2KMnO₄ + MnO₂ + 4KOH

Purification:

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The purple crystals of potassium permanganate are isolated and purified.

Storage and Handling

Potassium permanganate should be stored in a cool, dry place, away from organic materials and reducing agents. Handle with care, as it can cause burns and is reactive with many substances.

FAQs

Permanganate is an excellent oxidizer. Why?

Elements grow more electronegative as their oxidation states increase. As a result, permanganate is an excellent oxidising agent.

What colour does potassium permanganate have?

The physical state of potassium permanganate is an odourless solid that resembles dark purple or bronze crystals. The solution turns purple when these crystals are dissolved in water.

What makes KMnO4 a self-indicator?

When all of the permanganate ions were being used up in the reaction, the solution sheds its pink colour. Potassium permanganate is a self-indicator because it acts as an indication in addition to being one of the reactants.