Reduction of the metal centre in aqueous permanganate ion involves

Reduction of the metal centre in aqueous permanganate ion involves
  1. three electrons in neutral medium
  2. five electrons in neutral medium
  3. three electrons in alkaline medium
  4. five electrons in acidic medium

Solution

In neutral medium: $\quad \mathrm{MnO}_4^{-} \rightarrow \mathrm{MnO}_2\left(\mathrm{Mn}^{7+}+3 e^{-} \rightarrow \mathrm{Mn}^{4+}\right)$ In alkaline medium : $\quad \mathrm{MnO}_4^{-} \rightarrow \mathrm{MnO}_2\left(\mathrm{Mn}^{7+}+3 \varepsilon^{-} \rightarrow \mathrm{Mn}^{4+}\right)$ In acidic medium : $\quad \mathrm{Mn}_4^{-} \rightarrow \mathrm{Mn}^{2+}\left(\mathrm{Mn}^{7+}+5 e^{-} \rightarrow \mathrm{Mn}^{2+}\right)$

Asked in: JEE Advanced 2011 (Paper 2)

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