Atomic Number : 15 Electronic Configuration : [Ne] 3s2 3p3 Group Number : 15 Periodic Number : 3
Oxides of phosphorus
I Phosphorus trioxide P2O3 or P4O6
It is obtained by the combustion of phosphorus in a limited supply of air.
4P + 3O2 ® 2P2O3
1. It is a white waxy substance
2. It has a garlic odour.
1. It reacts with cold water, gives phosphorus acid.
P2O3 +3H2O ® 2H3PO3
2. It reacts with hot water vigorously to form inflammable phosphine.
2P2O3 + 6H2O ® PH3 + 3H3 PO4
II Phosphorus pentoxide P2O5 or P4O10
Phosphorus pentoxide can be prepared by burning phosphorus with sufficient
supply of air.
P4 + 5O2 ®P4 O10
It is a white solid and an acidic oxide.
1. It reacts with moisture to form metaphosphoric acid.
P4O10 + 2H2O ® 4HPO3
When the solution is boiled, the metaphosphoric acid is changed to
HPO3 + H2O ® H3PO4
P4O10 + 6H2O ® 4H3 PO4
2. 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.