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Question
Indicate the steps in the preparation of KMnO4 from pyrolusite ore.
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Solution 1
Potassium permanganate can be made by the following methods:
It is produced industrially by the electrolytic oxidation of manganate(VI) followed by the alkaline oxidative fusion of MnO2.
\[\ce{MnO2 ->[{Fused with KOH, oxidised with air or KNO3}] \underset{{manganate ion}}{MnO^{2-}_4}}\]
\[\ce{\underset{{manganate ion}}{MnO^{2-}_4} ->[{Electrolytic oxidation in alkaline solution}] \underset{{permanganate ion}}{MnO^-_4}}\]
The chemical reactions of acidic potassium permanganate with SO2 are as follows –
\[\ce{2MnO4 + 2H2O + 5SO2 -> 2Mn^{2+} + 4H^+ + 5SO^{2-}_4}\]
Solution 2
\[\ce{2MnO2 + 4KOH + O2 ->[\Delta] 2K2MnO4 + 2H2O}\]
\[\ce{3MnO^2-_4 + 4H+ -> 2MnO^-_4 + MnO2 + 2H2O}\]
Notes
Students can refer to the provided solutions based on their preferred marks.
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