Permanganate

A permanganate is the general name for a chemical compound containing the manganate(VII) ion, (MnO₄−). Because manganese is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion has tetrahedral geometry. Permanganate solutions are purple in color and are stable in neutral or slightly alkaline media.The exact chemical reaction is dependent upon the organic contaminants present and the oxidant utilized. For example, trichloroethene (C₂HCl₃) is oxidized by sodium permanganate to form carbon dioxide (CO₂), manganese dioxide (MnO₂), sodium ions (Na+), hydronium ion (H+), and chloride ions (Cl-)

In an acidic solution, permanganate(VII) is reduced to the colourless +2 oxidation state of the manganese(II) (Mn2+) ion.

8 H+ + MnO₄− + 5 e− → Mn2+ + 4 H₂O

In a strongly basic solution, permanganate(VII) is reduced to the green +6 oxidation state of the manganate MnO₄2−.

MnO₄− + e− → MnO₄2−

In a neutral medium however, it gets reduced to the brown +4 oxidation state of manganese dioxide MnO₂.

2 H₂O + MnO₄− + 3 e− → MnO₂ + 4 OH−