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Describe the preparation of potassium permanganate. How doe the acidified permanganate solution react with (i) iron (II) ions (ii) SO_(2) and (iii) oxalic acid? Write the ionic equations for the reactions. |
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Answer» Solution :PREPARATION of potassium permanganate: (i) Reaction with Fe(II) ions: Oxidation half reaction: `5Fe^(2+) rarr 5Fe^(3+) + 5e^(-)` Reduction half reaction: `MnO_(4)^(-) + 8H^(+) + 5e^(-) rarr Mn^(2+) + 4H_(2)O` Net reaction: `5Fe^(2+) + MnO_(4)^(-) + 8H^(+) rarr 5Fe^(2+) + MnO_(4)^(-) + 7H_(2)O` (ii) Sulphur dioxide `(SO_(2))`: Oxidation half reaction: `5SO_(2) + 10H_(2)O rarr 5SO_(4)^(2-) + 2OH^(+) + 10e^(-)` Reduction half reaction: `MnO_(4)^(-) + 8H^(+) + 5e^(-) rarr Mn^(2+) + 4H_(2)O xx 2` Net reaction: `5SO_(2) +2MnO_(4)^(-) + 2H_(2)O rarr 5SO_(4)^(2-) + 2Mn^(2+) + 4H^(+)` (III) Oxalic acid: Oxidation half reaction: `5C_(2)O_(4)^(2-) rarr 10CO_(2) + 10e^(-)` Reduction half reaction: `MnO_(4)^(-)+ 8H^(+) + 5e^(-) rarr Mn^(2+) + 4H_(2)O xx 2` Net reaction: `5C_(2)O_(4)^(2-) + 2MnO_(4)^(-) + 16H^(+) rarr 2Mn^(2+) + 10CO_(2) + 8H_(2)O` |
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