3 MnO42- + 4 H3O+ → 2 MnO4- + MnO2 + 6 H2O

This is an oxidation-reduction (redox) reaction:

2 MnVI - 2 e- → 2 MnVII (oxidation)

MnVI + 2 e- → MnIV (reduction)

MnO42- is both an oxidizing and a reducing agent (disproportionation (dismutation)).

Reactants:

  • MnO42-
  • H3O+
    • Names: Hydronium source: wikidata, accessed: 2019-09-07, Hydroxonium source: wikidata, accessed: 2019-09-07, H3O(+) source: wikidata, accessed: 2019-09-07

Products:

  • MnO4-
  • MnO2 – Manganese oxide source: wikipedia, accessed: 2019-09-27, Manganese(IV) oxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: Manganese dioxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Pyrolusite source: wikipedia, accessed: 2019-09-27, Hyperoxide of manganese source: wikipedia, accessed: 2019-09-27
    • Appearance: Brown-black solid source: wikipedia, accessed: 2019-09-27; Black-to-brown powder source: ICSC, accessed: 2019-09-04
  • H2O – Water, oxidane source: wikipedia, accessed: 2019-09-27
    • Other names: Water (H2O) source: wikipedia, accessed: 2019-09-27, Hydrogen hydroxide (HH or HOH) source: wikipedia, accessed: 2019-09-27, Hydrogen oxide source: wikipedia, accessed: 2019-09-27
    • Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas source: wikipedia, accessed: 2019-09-27