Question

The `Mn^(3+)` ion is unstable in solution and undergoes disproportionation reaction to give `Mn^(+2), MnO_(2)`, and `H^(o+)` ion. Write a balanced ionic equation for the reaction.

Answer 1

The skeleton equyation for the reation is :
`Mn^(3+)(aq)rarrMn^(2+)(aq)+MnO_(2)(s) +H^(+)(aq)`
Oxidation half reaction: `(overset(+3)Mn)^(3+)rarroverset(+4)MnO(2)`
(i) Add one `e^(-)` on the product side to balance change in O.N.
`(overset(+3)Mn)^(3+)rarroverset(+4)MnO_(2)+e^(-)`
(ii) Balance clarges by adding `4H^(+)`on the product side.
`Mn^(3+)rarrMnO_(2)+4H^(+)+e^(-)`
(iii) Balance oxygen atoms by adding two molecules of `H_(2)OrarrMnO_(2)+4H^(+)e^(-)`
Reduction half reaction: `(overset(+3)Mn)^(3+)rarr(overset(+2)Mn)^(2+)`
Add one `e^(-)` on the reactatnt side to bal,ance change in O.N.
`Mn^(3+)+e^(-)rarrMn^(2+)`
Add the eqns representing the two half ractions, `{:(Mn^(3+)+2H_(2)OrarrMnO_(2)+4H^(+)+e^(-)),(Mn^(3+)+2H_(2)OrarrMn^(2+))/(2Mn^(3+)+2H_(2)OrarrMnO_(2)+Mn^(2+)+4H^(+)):}`