Permanganate

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The structure of the manganate(VII) anion

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 manganate(VII) ion is a strong oxidizer.

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

16 H₃O ⁺ + 2 MnO₄⁻ + 10 Cl⁻ → 2 Mn²⁺ + 5 Cl₂ + 24 H₂O

6 H⁺ + 2 MnO₄⁻ + 5 HCOOH → 8 H₂O + 2 Mn²⁺ + 5 CO₂

In a basic solution, manganate(VII) is either reduced to the brown +4 oxidation state of MnO₂ or to the green +6 oxidation state of MnO₄²⁻.

4 OH⁻ + 2 MnO₄⁻ + 3 C₂O₄²⁻ → 2 MnO₂ + 6 CO₃²⁻ + 2 H₂O

3 OH⁻ + 2 MnO₄⁻ + HSO₃⁻ → 2 MnO₄²⁻ + SO₄²⁻ + 2 H₂O

1 Production
2 Properties
3 Compounds
4 External links

[edit] Production

Permanganates may be produced by oxidation of manganese compounds by strong oxidizing agents, for instance, sodium hypochlorite or lead dioxide:

2 MnCl₂ + 5 NaClO + 6 NaOH → 2 NaMnO₄ + 9 NaCl+ 3 H₂O

2 MnSO₄ + 5 PbO₂+ 3 H₂SO₄ → 2 HMnO₄+ 5 PbSO₄ + 2 H₂O

Or by dismutation of manganates:

3 Na₂MnO₄ + 2 H₂O → 2 NaMnO₄ + MnO₂ + 4 NaOH

[edit] Properties

Manganates(VII) are salts of permanganic acid. Manganate(VII) is a strong oxidizer, and similar to perchlorate. It is therefore in common use in qualitative analysis that involves redox reactions(permanganometry).Besides this, it is stable.

It is a useful reagent, though with organic compounds, it may just destroy them entirely.

Manganates(VII) are not very thermically stable. For instance, potassium permanganate decomposes at 230 °C:

2 KMnO₄ → K₂MnO₄ + MnO₂ + O₂