Question

Discuss the method of preparation of potassium permanganate from pyrolusite and write the structural formula of permanganate ion.

Hint:

Potassium permanganate is synthesized via oxidation of manganese dioxide followed by disproportionation in acidic medium.

Answer 1

Step 1: Potassium permanganate (\( KMnO_4 \)) is prepared from pyrolusite (\( MnO_2 \)) via the following steps: 

Step 2: Oxidation of Pyrolusite: \[ 2 MnO_2 + 4 KOH + O_2 \rightarrow 2 K_2MnO_4 + 2 H_2O \] 

Step 3: Disproportionation of Manganate: \[ 3 K_2MnO_4 + 2 H_2O \rightarrow 2 KMnO_4 + MnO_2 + 4 KOH \] 

Step 4: The structural formula of the permanganate ion (\( MnO_4^- \)): \[ \text{A tetrahedral structure with Mn in +7 oxidation state.} \]