Question

How Potassium Permanganate (${\mathrm{KMnO}}_4$) Formed?

Answer 1

Potassium permanganate(${\mathrm{KMnO}}_4$) is an oxidising agent with disinfectant, deodorising, and astringent properties.

• It is an inorganic compound.
• It is a purplish-black crystalline salt.
• It is odorless and it is easily dissolves in ethanol and organic solvents.
• It is used for a number of skin conditions.
• It is used in the water treatment industry.

Formation of Potassium permanganate $\left({\mathrm{KMnO}}_4\right)$: Potassium permanganate is prepared from pyrolusite ore, which involves some steps:

Step 1: The conversion of ${\mathrm{MnO}}_2$ to potassium manganate. Potassium permanganate is prepared by mixing a solution of KOH and powdered manganese oxide with oxidizing agents such as potassium chlorate. The mixture is evaporated and boiled and the residue is heated in an iron skillet until it attains a pasty consistency.

$\underset{(\mathrm{manganese}\mathrm{dioxide})}{3{\mathrm{MnO}}_2\left(\mathrm{s}\right)}+\underset{(\mathrm{potassium}\mathrm{hydroxide})}{6\mathrm{KOH}\left(\mathrm{s}\right)}+\underset{(\mathrm{Potassium}\mathrm{chlorate})}{6{\mathrm{KClO}}_3\left(\mathrm{aq}\right)}\stackrel{∆}{\to }\underset{(\mathrm{Potassium}\mathrm{manganate})}{3{\mathrm{K}}_2{\mathrm{MnO}}_4\left(\mathrm{s}\right)}+\underset{(\mathrm{Potassium}\mathrm{chloride})}{6\mathrm{KCl}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{water}\right)}{3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

Step 2: Oxidation of potassium manganate to potassium permanganate. The potassium manganate (green) thus formed is boiled with a large amount of water and a stream of chlorine, CO₂ and ozonated air is passed through the liquid until it is converted into permanganate. The formed MnO₂ is continuously removed to prevent permanganate from breaking down.

$\underset{(\mathrm{Potassium}\mathrm{manganate})}{3{\mathrm{K}}_2{\mathrm{MnO}}_4\left(\mathrm{s}\right)}\stackrel{}{+\underset{\left(\mathrm{chlorine}\right)}{3{\mathrm{Cl}}_2\left(\mathrm{g}\right)}\to }\underset{(\mathrm{Potassium}\mathrm{permanganate})}{3{\mathrm{KMnO}}_4\left(\mathrm{s}\right)}+\underset{(\mathrm{potassium}\mathrm{chloride})}{6\mathrm{KCl}\left(\mathrm{s}\right)}$