Chromium (III) Oxide

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Table Of Contents
  • Chromium (III) Oxide Identification
  • How is Chromium (III) Oxide Prepared
  • Reaction with Other Compounds
  • Properties and Characteristics of Chromium (III) Oxide
  • Uses
  • Is It Safe

Chromium (iii) oxide, commonly called chromia and referred to as oxo(oxochromiooxy)chromium in IUPAC nomenclature, is an inorganic compound containing chromium and oxygen represented by the chemical formula Cr2O3 [1]. It naturally occurs as the mineral eskolaite and is a highly insoluble compound with high thermal stability, having the properties of both an acid and a base [2, 3, 4].

Chromium (III) Oxide Identification

CAS Number 1308-38-9 [1]
PubChem CID 517277 [1]
ChemSpider ID 451305 [5]
UN Number 3077 [1]
EC Number 215-160-9 [1]
RTECS Number GB6475000 [1]
InChI Key QDOXWKRWXJOMAK-UHFFFAOYSA-N [1]

Chromium (III) Oxide Formula

How is Chromium (III) Oxide Prepared

It is produced through the reduction of sodium dichromate using sulfur at high temperatures indicated by the redox reaction [6]:

Na2Cr2O7 S → Na2SO4 Cr2O3

Ammonium dichromate, on heating, decomposes into chromium (iii) oxide, water, and nitrogen [7]:

(NH4)2Cr2O7 → Cr2O3 N2 4H2O

Chromium (iii) carbonate is heated to form chromium (iii) oxide and carbon dioxide:

Cr2(CO3)3 → Cr2O3 3CO2

Reaction with Other Compounds

Chromium (III) Oxide with Hydrochloric Acid

It reacts with dilute hydrochloric acid to form chromium (iii) chloride and water [8]:

Cr2O3 6HCl → 2CrCl3 3H2O

Chromium (III) Oxide with Hydrogen Sulfide

When chromium (iii) oxide reacts with gaseous hydrogen sulfide, it yields chromium (iii) sulfide and water:

Cr2O3 3H2S → Cr2S3 3H2O

Properties and Characteristics of Chromium (III) Oxide

General Properties

Molar Mass/Molecular Weight 151.989 g/mol [1, 3]

Physical Properties

Color and Appearance Dry, light or dark green, fine crystalline powder [1, 3]
Melting Point 2,435 °C, 4,415 °F [1]
Boiling Point 4,000 °C, 7,230 °F [1]
Density 5.22 g cm-3 [1, 3]
State of matter at room temperature Solid [1, 3]
Solubility Insoluble in acetone and alcohol, very slightly soluble in alkalies and acids [1]
Solubility in Water Practically insoluble, 2.96 µg/L (20 °C, pH 8), 3.13 µg/L (20 °C, pH 6) [1]
Magnetic Susceptibility (χ)  1960.0 X 10-6 cm3/mol

Atomic Properties

Crystal Structure Hexagonal

Chromium (III) Oxide

Uses

  • Because of its stability, chromium (iii) oxide is used as the green pigment in inks, glasses, and paints and as a colorant for ceramics, as well as producing a faint green tinge in glazes [8].
  • It serves as an abrasive for polishing or stropping the edges of razors, knives, and surfaces of optical devices [9].

Is It Safe

Exposure to chromium (iii) oxide through mouth and skin can cause acute toxicity [1]. It may cause an allergic skin reaction and serious eye damage [1]. It can also cause reproductive toxicity and is harmful to the unborn child [1].

References

  1. Chromium(III) Oxide – Pubchem.ncbi.nlm.nih.gov
  2. Chromium Oxide Powder (Cr2O3) – Reade.com
  3. Chromium(III) Oxide – Americanelements.com
  4. Chemistry of Chromium – Chem.libretexts.org
  5. Chromium(III) Oxide – Chemspider.com
  6. Chemical Equations – Chemequations.com
  7. Stoichiometry of Ammonium Dichromate Decomposition – Dartmouth.edu
  8. Chromium Oxide – Chromestarchemicals.com
  9. 5 Interesting Facts About Green Chrome Oxide – Basstechintl.com

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