Question

The starting material for the manufacture of $\;KMn{O_4}$ is:
(A) Pyrolusite
(B) Manganite
(C) Magnetite
(D) Haematite

Answer 1

Potassium permanganate is produced industrially from manganese dioxide which occurs as mineral pyrolusite. The $\;Mn{O_2}$ is fused with potassium hydroxide and heated in air or with another source of oxygen, like potassium nitrate or potassium chlorate.

Complete step by step solution:
The starting material for the manufacture of $\;KMn{O_4}$ is pyrolusite.
Pyrolusite is a mineral consisting essentially of manganese dioxide ($Mn{O_2}$) and is important as an ore of manganese. It is a black, amorphous appearing mineral, often with a granular, fibrous, or columnar structure, sometimes forming uniform crusts.
It consists of manganese ions and oxide ions.
Potassium permanganate is prepared by fusion of $Mn{O_2}$(pyrolusite) with potassium hydroxide and an oxidizing agent like $KN{O_3}$ to form potassium manganate (green mass), which disproportionate in a neutral or acidic solution to form permanganate.
$3{K_2}Mn{O_4} + 4HCl \to 2KMn{O_4} + Mn{O_2} + 2{H_2}O + 4KCl$

Hence, option A is correct.

Note: $\;KMn{O_4}$ is a strong oxidizing agent with Mn in +7 state. In an acidic medium there is a change of 5 electrons whereas in neutral and basic medium it will act as an oxidizing agent.