Preparation Of Potassium Permanganate

The preparation of potassium permanganate from the mineral pyrolusite proceeds in two stages. First, manganese dioxide is fused with potassium hydroxide and an oxidising agent to give the green potassium manganate, K_2MnO_4, in which manganese is in the +6 state. In the second stage, the manganate is converted to the purple permanganate, KMnO_4, with manganese in the +7 state, either by electrolytic oxidation or by disproportionation in neutral or acidic solution, where manganate(VI) changes into permanganate(VII) and manganese dioxide(IV). Thus the conversion is an oxidation or disproportionation step. The option of reduction in acidic medium is incorrect, since manganese is being raised from +6 to +7, an oxidation. The option of neutralisation does not change oxidation state. The option of simple dissolution involves no chemical change. This preparation is a standard NCERT d-block process. Examiners frequently test whether a student can connect potassium manganate with the underlying principle rather than merely recalling an isolated fact. Understanding preparation of potassium permanganate in this way ties directly into the wider study of d- and f-block elements, where the same reasoning recurs across many problems. Plausibility check: the increase in oxidation state from +6 in manganate to +7 in permanganate confirms that the conversion is an oxidation or disproportionation, not a reduction.