The Mn3+ ion is unstable in solution and undergoes disproportionation to give Mn2+.MnO2 and H+ ion. Write a balanced ionic equation for the reaction.
The given reaction can be represented as:
Mn3+(aq)⟶Mn2+(aq)+MnO2(s)+H+(aq)
The oxidation half equation is:
+3Mn3+(aq)⟶+4MnO2(s)
The oxidation number is balanced by adding on electron as:
Mn3+(aq)⟶MnO2(s)+e−
The charge is balanced by adding 4H+ ions as:
Mn3+(aq)+2H2O(l)⟶MnO2(s)+4H+(aq)+e− ⋯(i)
The reduction half equation is:
Mn3+(aq)⟶Mn2+(aq)
The oxidation number is balanced by adding one electron as:
Mn3+(aq)+e−⟶Mn2+(aq) ⋯(ii)
The balanced chemical equation can be obtained by adding equation (i) and (ii) as:
2Mn3+(aq)+2H2O(l)⟶MnO2(s)+Mn2+(aq)+4H+(aq)