Arsenic pentoxide

A 3D-model of arsenic pentoxide.

Arsenic pentoxide, also known as arsenic(V) oxide, is a chemical compound. Its chemical formula is As₂O₅. It has arsenic and oxide ions in it. The arsenic is in its +5 oxidation state. More common is arsen in its oxidation state +3 as As₂O₃ (arsenic trioxide or arsenic(III) oxide). The LD50 for arsenic pentoxide is 8mg/kg for rats.^[1] When the substance becomes wet, it turns into arsenic acid, which corrodes metals.

Properties

Arsenic pentoxide is a white, odourless solid.^[1] It dissolves easily in water to make arsenic acid. It is highly toxic, as are almost all arsenic compounds.^[1][2][3] It is a powerful oxidizing agent. It reacts with hydrochloric acid to make chlorine. As₂O₅ breaks down to arsenic trioxide and oxygen when heated to about 300°C.^[4]

${\displaystyle As_{2}O_{5}+268.1kJ\rightarrow As_{2}O_{3}+O_{2}}$

It reacts with bases to make arsenates. The energy for the reaction is taken from the heating.

Preparation

Arsenic pentoxide cannot be produced by burning arsen. That only results in As₂O₃. To produce arsenic pentoxid, arsenic acid will be dehydrated. This is done with phosphorus(V) oxide.

${\displaystyle 2H_{3}AsO_{4}\rightleftharpoons As_{2}O_{5}+3H_{2}O}$

The arsenic pentoxide drops out as white powder.^[5]

Uses

Arsenic pentoxide is used to make pesticides and insecticides. It is also used in glass industry.^[6]

Related pages

• Arsenic pentafluoride
• Arsenous acid
• Phosphorus pentoxide
• Antimony pentoxide

References

1. "ARSENIC PENTOXIDE". chemicalland21.com. 2012 [last update]. Retrieved 6 August 2012.
2. Hudson, T. G. (2012) [last update]. "Toxicity of Arsenic Compounds". Ncbi.NLM.nih.gov. 20 (3): 251. PMC 1039212.
3. "ARSENIC Toxicity". manbir-online.com. 2012 [last update]. Retrieved 6 August 2012.
4. Wiberg, Nils; Arnold Holleman (2007). Lehrbuch der Anorganischen Chemie. Berlin, New York: de Gruyter. p. 845. ISBN 978-3-11-017770-1.
5. Wiberg, Nils; Arnold Holleman (2007). Lehrbuch der Anorganischen Chemie. Berlin, New York: de Gruyter. p. 844. ISBN 978-3-11-017770-1.
6. "Arsenic pentoxide Manufacturers Suppliers in China CAS No 1303-28-2 | Xilan Chemicals Co Ltd Leading Chemical Manufacturer and Trader". xilanchem.com. 2012 [last update]. Retrieved 6 August 2012.^{[permanent dead link]}