What is the correct order of following steps in the preparation of potassium permanganate?
(A) disproportionation in a neutral or acidic solution
(B) production of dark green $K_2MnO_4$
(C) $MnO_2$
(D) fusion with alkali metal hydroxide and $KNO_3$
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (C), (D), (B), (A)
Preparation of $KMnO_4$ is done from $MnO_2$ in two major stages:
Step 1: Oxidation of $MnO_2$ to manganate $(K_2MnO_4$) by fusion with KOH and an oxidizing agent like $KNO_3$
Step 2: Conversion of manganate into permanganate by disproportionation in acidic or neutral medium
Option 2: (C), (D), (B), (A)
This starts correctly with $MnO_2$ as the raw material.
It is fused with alkali metal hydroxide and $KNO_3$ which oxidizes $MnO_2$.
This produces dark green $K_2MnO_4$.
Finally, manganate undergoes disproportionation in acidic or neutral solution to form $KMnO_4$.
Thus, this is the correct preparation sequence.