2 Cr (s) + 3 O2 (g) → 2 CrO3 (aq)

This is an oxidation-reduction (redox) reaction:

2 Cr0 - 12 e- → 2 CrVI (oxidation)

6 O0 + 12 e- → 6 O-II (reduction)

Cr is a reducing agent, O2 is an oxidizing agent.

Reactants:

  • Cr
    • Names: Chromium source: wikidata, accessed: 2019-09-07source: ICSC, accessed: 2019-09-04source: NIOSH NPG, accessed: 2019-09-02, Chromium metal source: NIOSH NPG, accessed: 2019-09-02, Cr source: wikidata, accessed: 2019-09-07
    • Appearance: Grey powder source: ICSC, accessed: 2019-09-04; Blue-white to steel-gray, lustrous, brittle, hard, odorless solid. source: NIOSH NPG, accessed: 2019-09-02
  • O2
    • Names: Dioxygen source: wikidata, accessed: 2019-09-07, Oxygen source: ICSC, accessed: 2019-09-04source: wikidata, accessed: 2019-09-07, Oxygen (liquefied) source: ICSC, accessed: 2019-09-04
    • Appearance: Odourless compressed gas source: ICSC, accessed: 2019-09-04; Liquefied gas. colourless-to-blue extremely cold liquid source: ICSC, accessed: 2019-09-04

Products:

  • CrO3 – Chromium trioxide source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02
    • Other names: Chromic anhydride source: wikipedia, accessed: 2019-09-27source: wikidata, accessed: 2019-09-02source: ICSC, accessed: 2019-09-04, Chromium(VI) oxide source: wikipedia, accessed: 2019-09-27, Chromic acid (misnomer) source: wikipedia, accessed: 2019-09-27
    • Appearance: Dark red granular solid, deliquescent source: wikipedia, accessed: 2019-09-27; Odourless dark red deliquescent crystals, flakes or granular powder source: ICSC, accessed: 2019-09-04