Question

How is ${\mathrm{KMnO}}_4$ prepared from pyrolusite ore?

Answer 1

Preparation of Potassium Permanganate

• Potassium Permanganate $\left({\mathrm{KMnO}}_4\right)$ is prepared from Pyrolusite ore $\left({\mathrm{MnO}}_2\right).$
• The finely powdered Pyrolusite ore$\left({\mathrm{MnO}}_2\right).$ is fused with an alkali metal hydroxide like $\mathrm{KOH}$in the presence of air or an oxidizing agent like ${\mathrm{KNO}}_3.$
• The oxidizing agent oxidizes pyrolusite to give the dark green potassium Manganate $\left({\mathrm{K}}_2{\mathrm{MnO}}_4\right)$.
• Potassium manganate undergoes different reactions in a neutral or acidic solution to give potassium permanganate.
• The reaction of in basic medium is given below

$\underset{\mathrm{Manganese}\mathrm{oxide}}{2{\mathrm{MnO}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Potassium}\mathrm{hydroxide}}{4\mathrm{KOH}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Potassium}\mathrm{manganate}}{2{\mathrm{K}}_2{\mathrm{MnO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• Further Potassium magnate undergoes electrolysis to form Potassium permanganate.
• The overall reaction is given below
• $\underset{\mathrm{Potassium}\mathrm{manganate}}{2{\mathrm{K}}_2{\mathrm{MnO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}}\stackrel{}{\left(\mathrm{aq}\right)\stackrel{\mathrm{Electrolysis}}{\to }\underset{\mathrm{Potassium}\mathrm{permanganate}}{2{\mathrm{KMnO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{Potassium}\mathrm{hydroxide}}{2\mathrm{KOH}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2}}\left(\mathrm{g}\right)$

Potassium permanganate is prepared from Pyrolusite ore by electrolysis of potassium magnate.