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The d & f Block Elements — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryThe d & f Block Elements3 Marks
Question
Indicate the steps in the preparation of:
KMnO4 from pyrolusite ore.
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Answer

Pottassium Permanganate (KMnO4) is prepared from Pyrolusite ore (MnO2). The finely powdered Pyrolusite ore (MnO2) is fused with an alkali metal hydroxide like KOH in the presence of air or an oxidizing agent like KNO3 to give the dark green potassium Manganate (K2MnO4). Potassium manganate disproportionate in a neutral or acidic solution to give potassium permanganate.
$2\text{MnO}_2+4\text{KOH}+\text{O}_2\rightarrow2\text{K}_2\text{MnO}_4+2\text{H}_2\text{O}$
$3\text{MnO}^{2-}_4+4\text{H}^+\rightarrow2\text{MnO}^-_4+\text{MnO}_2+2\text{H}_2\text{O}$
Commercially potassium permanganate is prepared by the alkaline oxidative fusion of Pyrolusite ore (MnO2) followed by the electrolytic oxidation of manganate (4) ion.
$2\text{MnO}_2+4\text{KOH}+\text{O}_2\rightarrow2\text{K}_2\text{MnO}_4+2\text{H}_2\text{O}$

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