Question

How will you obtain pure potassium permanganate ( $KMn{{O}_{4}}$ ) crystals from its ore, pyrolusite? Give the steps involved and the reactions.

Answer 1

Hint: Pyrolusite is an ore containing manganese dioxide mineral. There are two steps involved in the extraction of potassium permanganate ( $KMn{{O}_{4}}$ ) from its ore pyrolusite. The molecular formula of manganese dioxide is $Mn{{O}_{2}}$, contains manganese metal and two oxygen atoms.

Complete step by step solution:
- As we know that extraction of potassium permanganate is a two-step process.
Step-1:
In this step, manganese dioxide is going to be fused with potassium hydroxide (KOH) in presence of oxygen and forms potassium manganate. The chemical reaction is as follows.
\[2Mn{{O}_{2}}+4KOH+{{O}_{2}}\xrightarrow{Fuse}2{{K}_{2}}Mn{{O}_{4}}+2{{H}_{2}}O\]
- In the above reaction 2 moles of manganese dioxide reacts with 4 moles of potassium hydroxide in presence of oxygen forms 2 moles of potassium manganate as the product.
Step-2:
- The formed potassium manganate in the step-1 undergoes oxidation reaction with chlorine and forms potassium permanganate. The chemical reaction is as follows.
\[{{K}_{2}}Mn{{O}_{4}}+C{{l}_{2}}\xrightarrow{oxidation}2KMn{{O}_{4}}+2KCl\]
- In the above reaction one mole of potassium manganate reacts with one mole of chlorine and forms 2 moles of potassium permanganate and potassium chloride as the products.
- After the preparation of potassium permanganate we have to do the crystallization and the crystals formed are separated and dried.

Note: Potassium permanganate is an inorganic chemical and soluble in water. It is also called a permanganate of potash or Condy’s crystal. Potassium manganate is dark green in colour and the colour of potassium permanganate is purple. Potassium permanganate is used as an oxidizing agent in various chemical reactions.