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.
A. `3Mn^(3+)+4H_(2)O rarr MnO_(2)+Mn^(2+)+8H^(+)`
B. `Mn^(2+)+4H_(2)O rarr MnO_(2) + 4H^(+)`
C. `Mn+2H_(2)O rarr MnO_(2) + 4H^(+)`
D. `2 M n^(3+)+2H_(2)O rarr MnO_(2)+Mn^(2+)+4H^(+)`

Answer 1

Correct Answer - D
Skeletal equation is `Mn^(3+)rarr Mn^(2+)+MnO_(2)+H^(+)`
Oxidation half equation : `Mn^(3+)rarr overset(+4)MnO_(2)`
or `Mn^(3+)+2H_(2)O rarr MnO_(2)+4H^(+)+e^(-)` ... (i)
Reduction half equation : `Mn^(3+)rarr Mn^(2+)`
or `Mn^(3+)+e^(-) rarr Mn^(2+)` ...(ii)
Adding eq. (i) and (ii) the balanced equation is
`2Mn^(3+)+2H_(2)O rarr MnO_(2)+Mn^(2+)+4H^(+)`