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Phosphorus forms a number of oxoacids. They are hypophosphorous acid (H3PO2), Phosphorous acid (H3PO3), Hypophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7) and meta phosphoric acid (HPO2)n. 1. Hypo phosphorous acid (H3PO2) or phosphinic acid It is preapred by the oxidation of phosphine by iodine in the presence of calculated amount of water. It is a monobasic acid. PH3 + 2I2 + 2H2O -----------> H3PO2 + 4 HI 2. Phosphorous acid (H3PO3) or phosphonic acid It is prepared by hydrolysis of phosphorous trioxide (P4O6). Phosphorous acid is dibasic. P4O6 + 6H2O ----------> 4H3PO3 3. Hypophosphoric acid (H4P2O6) It is prepared by controlled oxidation of red phosphorous with sodium chlorite solution, when disodium salt of hypophosphoric acid is formed which then passing through cation exchanger yield hypophosphoric acid. Hypophosphoric acid is tetrabasic. 2P + 2NaClO2 + 2H2O ---------> Na2H2P2O6 + 2HCl Na2H2P2O6 + 2H -----resin-----> H4P2O6 + 2Na - resin 4. Orthophosphoric a...

In the laboratory phosphine is prepared by heating white phosphorus with concentrated caustic alkali solution in an inert atmosphere of oil gas or CO2. P4 + 3NaOH + 3H2O ------------> 3NaH2PO2 (Sodium hypophosphite) + PH3 (phosphine) Metal phosphides on hydrolysis form phosphine Ca3P2 + 6H2O ------------> 3Ca(OH)2 + 2PH3 A pure sample of phosphine can also be prepared by heating phosphorous acid 4H3PO3 ---------------> 3H3PO4 + PH3 Phosphine has pyramidal structure and is a weaker base than NH3

The main oxides of phosphorus are phosphorus trioxide (P4O6) and phosphorus pentoxide (P4O10) . Phosphorous trioxide is regarded as the anhydride of phosphorous acid (H3PO4). phosphorus trioxide (P4O6) is prepared by heating phosphorous in limited supply of oxygen. P4O10 is prepared by burning white phosphorous in excess of air or oxygen. P4 + 3O2 -------------> P4O6 P4 + 5 O2 ------------> P4O10 P4O10 has great affinity for water and hence it is used as a dehydrating agent. It can dehydrate HNO3 and H2SO4 to yield N2O5 and SO3 respectively. 2H2SO4 + P4O10 ------------> 2SO3 + 4HPO3 P4O6 and P4O10 dissolves in water to give phosphorus acid and orthophosphoric acid respectively. P4O6 + 6H2O -------------> 4H3PO3 P4O10 + 6H2O --------------> 4H3PO4 Related article oxyacids of phosphorus