Laboratory Preparation of Phosphorus Pentoxide

Phosphorus pentoxide P2O5 or P4O10 can be prepared by burning phosphorus with sufficient supply of air.

P4 + 5O2 →P4 O10


Physical properties

It is a white solid and an acidic oxide.

Chemical properties

  1. It reacts with moisture to form metaphosphoric acid.

P4O10 + 2H2O → 4HPO3

When the solution is boiled, the metaphosphoric acid is changed to orthophosphoric acid.

HPO3 + H2O → H3PO4

or,  P4O10 + 6H2O → 4H3PO4

  1. Phosphorus pentoxide extracts water from many inorganic compound including sulphuric acid, nitric acid and several organic compounds. It is therefore, used as a powerful dehydrating agent.


Use: It is used as a dehydrating agent.