Arsenic pentoxide

Arsenic pentoxide
Other names Arsenic(V) oxide Arsenic oxide Arsenic anhydride
Identifiers
CAS number	1303-28-2 Y
PubChem	14771
ChemSpider	14088 Y
EC number	215-116-9
RTECS number	CG2275000
Jmol-3D images	Image 1
SMILES O=[As](=O)O[As](=O)=O
InChI InChI=1S/As2O5/c3-1(4)7-2(5)6 Y Key: COHDHYZHOPQOFD-UHFFFAOYSA-N Y InChI=1/As2O5/c3-1(4)7-2(5)6 Key: COHDHYZHOPQOFD-UHFFFAOYAN
Properties
Molecular formula	As2O5
Molar mass	229.8402 g/mol
Appearance	white hygroscopic powder
Density	4.32 g/cm3
Melting point	315 °C (decomposes)
Solubility in water	59.5 g/100 mL (0 °C) 65.8 g/100 mL (20 °C) 8.20 g/100 mL (100 °C)
Solubility	soluble in alcohol
Acidity (pKa)	7
Hazards
EU classification	Very toxic (T+) Carc. Cat. 1 Dangerous for the environment (N)
R-phrases	R45, R23/25, R50/53
S-phrases	S53, S45, S60, S61
NFPA 704	0 4 0
LD50	8 mg/kg (rat, oral)
Related compounds
Other cations	Phosphorus pentoxide Antimony pentoxide
Related compounds	Arsenic trioxide Arsenic acid
Y pentoxide (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Arsenic pentoxide is the inorganic compound with the formula As₂O₅. This glassy, white solid is relatively unstable, consistent with the rarity of the As(V) oxidation state. More common, and far more important commercially, is arsenic(III) oxide (As₂O₃).

Synthesis and reactions

Arsenic pentoxide can be crystallized by heating As₂O₃ under oxygen. In fact, arsenic pentoxide decomposes to oxygen and As₂O₃ upon heating.^[1]

As₂O₅, which like phosphorus pentoxide is hygroscopic, dissolves readily in water to form arsenic acid, H₃AsO₄.^[2]

References

1. ^ Martin Jansen (1977). "Crystal Structure of As₂O₅". Angewandte Chemie International Edition in English 16 (5): 314–315. doi:10.1002/anie.197703142. 
2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419.  pp. 576-577

External links

• NIOSH Pocket Guide to Chemical Hazards
• IARC Monograph – Arsenic and Arsenic Compounds
• NTP Report on Carcinogens – Inorganic Arsenic Compounds
• ESIS: European chemical Substances Information System
• Institut national de recherche et de sécurité (1992). "Arsenic et composés minéraux." Fiche toxicologique n° 192. Paris:INRS. (French)
• Linstrom, P.J.; Mallard, W.G. (eds.) NIST Chemistry WebBook, NIST Standard Reference Database Number 69. National Institute of Standards and Technology, Gaithersburg MD. http://webbook.nist.gov