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प्रश्न
Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with oxalic acid? Write the ionic equation for the reaction.
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उत्तर
Potassium permanganate is prepared by the fusion of MnO2 with an alkali metal hydroxide and an oxidising agent like KNO3. This produces the dark green K2MnO4, which disproportionates in a neutral or acidic solution to give permanganate.
\[\ce{2MnO2 + 4KOH + O2 -> 2K2MnO4 + 2H2O}\]
\[\ce{3MnO^{2-}_4 + 4H+ -> 2MnO^-4 + MnO2 + 2H2O}\]
In an acidic medium (dilute sulphuric acid), permagnate ion reacts with oxalate ion \[\ce{(C2O^{2-}_4)}\] or oxalic acid at 333 K to evolve carbon dioxide gas.
Reduction half-reaction: \[\ce{[MnO^-_4 + 8H+ + 5e- -> Mn^{2+} + 4H2O] \times 2}\]
Oxidation half-reaction: \[\ce{[C2O^-_4 -> 2CO2 + 2e-] \times 5}\]
Net ionic equation: \[\ce{2MnO^-_4 + 16H+ + 5C2O^{2-}_4 -> 2Mn^{2+} + 8H2O + 10CO2}\]
संबंधित प्रश्न
Complete the following equation:
\[\ce{2MnO4- + 6H+ + 5NO2- ->}\]
When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow-coloured compound (A) is obtained, which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms an orange coloured crystalline compound (C).
(i) Write the formulae of the compounds (A), (B) and C.
(ii) Write one use of compound (C).
Complete the following equations : 2 MnO2 + 4 KOH + O2 →
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Indicate the steps in the preparation of \[\ce{K2Cr2O7}\] from chromite ore.
