Reduction of the metal centre in aqueous permanganate ion involves

Options

A. 3 electrons in neutral medium
B. 5 electrons in neutral medium
C. 3 electrons in alkaline medium
D. 5 electrons in acidic medium.

Explanation

In neutral medium
`MnO_(4)^(-) + 2H_(2)O + 3e^(-) rarrMnO_(2) + 4OH^(-)`
In alkaline medium
`MnO_(4)^(-) + e^(-) rarr MnO_(4)^(2-)`
But `MnO_(4)^(2-)` is further reduced to `MnO_(2)` as shown below
`MnO_(4)^(2-) + 2H_(2)O + 2e^(-) rarr MnO_(2) + 4OH^(-)`
Complete reaction is
`MnO_(4)^(2-) + 2H_(2)O+ 3e^(-) rarr MnO_(2) + 4OH^(-)`
which is the same as that for neutral medium.
In acidic medium
`MnO_(4)^(-) + 8 H^(+) + 5e^(-) rarr Mn^(2+) + 4H_(2)O`
Hence, the number of electrons involved in the reduction of metal centre in aqueous `MnO_(4)^(-)` ion in neutral, alkaline and acidic media are 3,3 and 5 respectively.