Chromium trioxide

Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions and bright orange when wet. The substance dissolves in water accompanied by hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser, a mutagen, and a carcinogen.

Chromium trioxide

  Chromium, Cr
  Oxygen, O
Names
IUPAC name
Chromium trioxide
Other names
Chromic anhydride, Chromium(VI) oxide, Chromic acid (misnomer)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.014.189
PubChem CID
RTECS number
  • GB6650000
UNII
UN number 1463
  • InChI=1S/Cr.3O Y
    Key: WGLPBDUCMAPZCE-UHFFFAOYSA-N Y
  • InChI=1/Cr.3O/rCrO3/c2-1(3)4
    Key: WGLPBDUCMAPZCE-YFSAMUSXAF
SMILES
  • O=[Cr](=O)=O
Properties
CrO3
Molar mass 99.993 g·mol−1
Appearance Dark red granular solid, deliquescent
Odor Odorless
Density 2.7 g/cm3 (20 °C)
Melting point 197 °C (387 °F; 470 K)
Boiling point 250 °C (482 °F; 523 K)
decomposes
  • 164.8 g/(100 mL) (0 °C)
  • 169 g/(100 mL) (25 °C)
  • 172.6 g/(100 mL) (40 °C)
  • 198.1 g/(100 mL) (100 °C)
Solubility Soluble in H2SO4, HNO3, (CH3CH2)2O, CH3COOH, (CH3)2CO
Magnetic susceptibility (χ)
 +40·10−6 cm3/mol
Thermochemistry
Std molar
entropy (S⦵298)
 73.2 J/(mol·K)
Std enthalpy of
formation (ΔfH⦵298)
 −589.3 kJ/mol
Hazards
GHS labelling:
Danger
H271, H301+H311, H314, H317, H330, H334, H335, H340, H350, H361f, H372, H410
P210, P260, P280, P303+P361+P353, P304+P340+P310, P305+P351+P338
NFPA 704 (fire diamond)
4
0
2
OX
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 80 mg/kg (rats, oral)
Safety data sheet (SDS) ICSC 1194
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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