1. Oxy Compounds of Phosphorus Phosphorus (III) Oxide (P 4 O 6 ) and Phosphorus (V) Oxide (P 4 O 10 ) represent the two most common oxidation states for phosphorus, +3 and +5 Anhydride- any chemical compound obtained through the elimination of water from another compound. Phosphorus (V) Oxide- Anhydride of phosphoric acid (H 3 PO 4 ), a weak triprotic acid Phosphorus (III) Oxide- Anhydride of phosphorous acid (H 3 PO 3 ), a weak diprotic acid Both acids have a tendency to undergo condensation reactions when heated Condensation Reactions involve two or more molecules combining to form a larger molecule by eliminating a smaller molecule such as H 2 O

2. Phosphoric Acid in Detergents The phosphates in detergents are often in the form of sodium tripolyphosphate (Na 5 P 3 O 10 ) A typical detergent formulation contains 47% phosphate, 16% bleaches, perfumes, and abrasives; and 37% linear alkylsulfonate surfactant The phosphate ions form bonds with metal ions that keep the metal ions from interfering with the surfactant molecules The phosphates keep the pH above 7 and prevent the surfactant molecules from gaining an H + ion

3. Phosphoric Acid in Fertilizers Most of the phosphate rock that is mined is converted into fertilizers The Ca 3 (PO 4 ) 2 in phosphate rock is insoluble – It needs to be converted into a soluble form by treating the phosphate rock with phosphoric acid Ca 3 (PO 4 ) 2 (s) + 4H 3 PO 4 (aq)  3Ca +2 (aq) + 6H 2 PO 4 - (aq) – The solubility of Ca 3 (PO 4 ) 2 allows it to be assimilated by plants it can also be washed from the soil into bodies of water, thus contributing to water pollution

4. Phosphorus Compounds in Biological Systems There are phosphate groups in both DNA and RNA – These phosphate groups are responsible for the control of protein biosynthesis and transmission of genetic information – It also occurs in adenosine triphosphate (ATP), which stores energy in biological cells and has the structure

5. Carbonic Acid and Carbonates Carbon dioxide is moderately soluble in water The resultant solutions are moderately acidic from the formation of carbonic acid, a diprotic, weak acid – CO 2 (aq) + H 2 O (l) ⇌ H 2 CO 3 (aq) – Carbonic acid cannot be isolated as pure compound, they can be obtained by neutralizing carbonic acid solutions