Gujarat BoardEnglish MediumSTD 11 ScienceChemistryRedox Reactions2 Marks
Question
$\text{MnO}^{2-}_4$ undergoes disproportionation reaction in acidic medium but $\text{MnO}^-_4$ does not. Give reason.
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Answer
Disproportionation is a type of redox reaction in which a species is simultaneously reduced and oxidised forming two different products.
In $\text{MnO}^{2-}_4$, the oxidation state of manganese is +6. It can disproportionate to form $\text{MnO}^-_4$ and $\text{MnO}^{2-}_4.$
$3\text{MnO}^{2-}_4+4\text{H}^{+}\xrightarrow{ \ \ \ \ \ \ \ }\text{MnO}_2+2\text{MnO}^{-}_4+2\text{H}_2\text{O}$
However, the oxidation state of Mn in $\mathrm{MnO}_4^{-}$is +7 which is the maximum possible oxidation state of Mn (atomic number $25,1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^5 4 s^2$ ) and hence it cannot undergo disproportionation reaction.
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