What are the products of the reaction between phosphorus pentoxide and water?

Diphosphorus pentoxide, P₂O₅, is sometimes called "phosphoric anhydride" because it reacts with water to form phosphoric acid, H₃PO₄:

P₂O₅(s) + 3 H₂O() 2 H₃PO₄

The reaction releases a tremendous amount of heat and is quite violent. The solution often vaporizes and splashes out of the container, accompanied by choking white fumes. The P₂O₅ is corrosive and very toxic, and the concentrated droplets of phosphoric acid solution it sprays can cause permanent eye damage and severe burns. Don't try this at home. Please.

P₂O₅ is prepared by burning phosphorus in extremely dry air. Diphosphorus pentoxide dehydrates moist air and any material it comes into contact with. It is often used as a dehydrating agent used in the synthesis of organic materials.

Author: Fred Senese senese@antoine.frostburg.edu

Copyright © 1997-2005 by Fred Senese
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Last Revised 07/31/07.URL: http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/p2o5-hydration.shtml