Given below are the half -cell reactions
`Mn^(2+)+2e^(-) to Mn, E^(@)=-1.18V`
`Mn^(3+)+e^(-) to Mn^(2+), E^(@)=+1.51 V`
The `E^(@)` for `3Mn^(2+)to Mn+2Mn^(3+)` will be _________.

Options

A. `-2.69V`, the reaction will not occur
B. `-2.69V`, the reaction will occur
C. `-0.33V`, the reaction will not occur
D. `-0.33V`, the reaction will occur

Answer

A

Explanation

`Mn^(2+)overset(E_(1)^(0)+1.51V)toMn^(2+)overset(E_(2)^(0)=-1.18V)toMn`
`therefore` For `Mn^(2+)` disproportionation, `E^(o)=-1.51V-1.18V`
`=-2.69V lt 0`
Reaction is non-spontaneous.