2 (Cr)3+ + 4 OH- + 3 MnO2 → 2 CrO42- + 3 (Mn)2+ + 2 H2O

This is an oxidation-reduction (redox) reaction:

3 MnIV + 6 e- → 3 MnII (reduction)

2 CrIII - 6 e- → 2 CrVI (oxidation)

MnO2 is an oxidizing agent, Cr3+ is a reducing agent.

Reactants:

  • Cr3+
  • OH- – Hydroxide source: wikipedia, accessed: 2019-09-27
    • Other names: Hydroxide ion source: wikidata, accessed: 2019-09-07
  • 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

Products:

  • CrO42-
    • Mn2+
    • 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