Video: Oxidation states of manganese

Manganese(VII) in the form of the permanganate ion, can be reduced to manganese(VI), manganese(IV), and manganese(II) by the hydrogen sulfite (acidic solution) and sulfite (basic solution) ions. The product depends upon the pH of the solution.
Under very basic conditions, the green manganate ion is formed:

MnO4-(aq) + e- ® MnO42-(aq)
SO32-(aq) + 2 OH-(aq) ® SO42-(aq) + Hsub>2O(l) + 2 e-

Under slightly basic conditions, a deep brown precipitate of manganese(IV) oxide is formed:

MnO4-(aq) + 2 H2O(l) + 3 e- ® MnO2(s) + 4 OH-(aq)
SO32-(aq) + 2 OH-(aq) ® SO42-(aq) + H2O(l) + 2 e-

Under acidic conditions, the colorless manganese(II) ion is formed:

MnO4-(aq) + 8 H+(aq) + 5 e- ® Mn2+(aq) + 4 H2O(l)
HSO3-(aq) + H2O(l) ® SO42-(aq) + 3 H+(aq) + 2 e-