Q72 / 180 · AIIMS 2003 · Chemistry

$\mathrm{MnO}_4^{2-}(1$ mole) in neutral aqueous medium is disproportionated to

  • Correct answer
    A
    2/3 mole of $\mathrm{MnO}_4^{-}$and $1 / 3$ mole of $\mathrm{MnO}_2$
  • B
    $1 / 3$ mole of $\mathrm{MnO}_4^{-}$and $2 / 3 \mathrm{~mole}$ of $\mathrm{MnO}_2$
  • C
    $1 / 3$ mole of $\mathrm{Mn}_2 \mathrm{O}_7$ and $1 / 3 \mathrm{~mole}$ of $\mathrm{MnO}_2$
  • D
    $2 / 3 \mathrm{~mole}$ of $\mathrm{Mn}_2 \mathrm{O}_7$ and $1 / 3$ mole of $\mathrm{MnO}_2$.

Solution

$3 \mathrm{MnO}_4{ }^{2-}+2 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{MnO}_{2(s)}$ $+2 \mathrm{MnO}_4^{-}+4 \mathrm{OH}^{-}$ for one mole $$ \mathrm{MnO}_4^{2-}+\frac{2}{3} \mathrm{H}_2 \mathrm{O} \rightarrow \frac{1}{3} \mathrm{MnO}_{2(s)}+\frac{2}{3} \mathrm{MnO}_4^{-}+\frac{4}{3} \mathrm{OH}^{-} $$

Hence, the correct answer is option: 'A'.

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