Chromium(II) chloride

Chromium(II) chloride
Names
	IUPAC name Chromium(II) chloride
	Other names Chromous chloride
Identifiers
CAS Number	10049-05-5 (anhydrous) ; 13931-94-7 (tetrahydrate) ;
3D model (JSmol)	anhydrous: Interactive image; tetrahydrate: Interactive image;
ChemSpider	23252 ;
ECHA InfoCard	100.030.136
EC Number	233-163-3;
PubChem CID	24871;
RTECS number	GB5250000;
UNII	CET32HKA21 (anhydrous) ; Q781GP5E2W (tetrahydrate) ;
UN number	3077
CompTox Dashboard (EPA)	DTXSID20905548 ;
	InChI InChI=1S/2ClH.Cr/h21H;/q;;+2/p-2 Key: XBWRJSSJWDOUSJ-UHFFFAOYSA-L ; InChI=1/2ClH.Cr/h21H;/q;;+2/p-2 Key: XBWRJSSJWDOUSJ-NUQVWONBAQ;
	SMILES anhydrous: [Cr+2].[Cl-].[Cl-]; tetrahydrate: Cl[Cr-4](Cl)([OH2+])([OH2+])([OH2+])[OH2+];
Properties
Chemical formula	Cl2Cr
Molar mass	122.90 g·mol−1
Appearance	White to grey/green powder (anhydrous); blue solid (tetrahydrate)
Odor	Odorless
Density	2.88 g/cm3 (24 °C)
Melting point	824 °C (1,515 °F; 1,097 K) ; anhydrous; 51 °C (124 °F; 324 K); tetrahydrate, decomposes
Boiling point	1,302 °C (2,376 °F; 1,575 K) ; anhydrous
Solubility in water	Soluble
Solubility	Insoluble in alcohol, ether
Acidity (pKa)	2
Magnetic susceptibility (χ)	+7230·10−6 cm3/mol
Structure
Crystal structure	Orthorhombic (deformed rutile, anhydrous), oP6; Monoclinic (tetrahydrate)
Space group	Pnnm, No. 58 (anhydrous); P21/c, No. 14 (tetrahydrate)
Point group	2/m 2/m 2/m (anhydrous); 2/m (tetrahydrate)
Lattice constant	a = 6.64 Å, b = 5.98 Å, c = 3.48 Å (anhydrous) α = 90°, β = 90°, γ = 90°
Coordination geometry	Octahedral (Cr2+, anhydrous)
Thermochemistry
Heat capacity (C)	71.2 J/mol·K
Std molar; entropy (S⦵298)	115.3 J/mol·K
Std enthalpy of; formation (ΔfH⦵298)	−395.4 kJ/mol
Gibbs free energy (ΔfG⦵)	−356 kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H319, H335
Precautionary statements	P261, P305+P351+P338
NFPA 704 (fire diamond)	2 0 1
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	1870 mg/kg (rats, oral)
Safety data sheet (SDS)	Oxford MSDS
Related compounds
Other anions	Chromium(II) fluoride; Chromium(II) bromide; Chromium(II) iodide
Other cations	Chromium(III) chloride; Chromium(IV) chloride; Molybdenum(II) chloride; Tungsten(II) chloride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Chromium(II) chloride describes inorganic compounds with the formula Cr Cl₂(H₂O)_n. The anhydrous solid is white when pure, however commercial samples are often grey or green; it is hygroscopic and readily dissolves in water to give bright blue air-sensitive solutions of the tetrahydrate Cr(H₂O)₄Cl₂. Chromium(II) chloride has no commercial uses but is used on a laboratory-scale for the synthesis of other chromium complexes.