Phosphoric acid

Phosphoric acid, H3PO₄, more correctly called orthophosphoric acid, is the most common of the phosphoric acids and is one the six strong acids. It can be produced from the hydrolysis of its acid anhydride phosphorus(V) oxide, P₄O₁₀, also called tetraphosphorus decoxide. Organic polyphosphates serve as energy reserviors in living systems.

physical properties

Phosphoric acid is a triprotic acid, in that all three protons can be dissociated. However, the third proton is not very acidic. The chemical formula can also be written as (HO)₃P=O, which more clearly indicates that each of the protons is bound to an oxygen atom.

H₃PO₄ <--> H⁺ + H₂PO₄^- &nbsp&nbsp&nbsp&nbsp K₁ = 7.5 x 10^-3

H₂PO₄^- <--> H⁺ + HPO₄^2- &nbsp&nbsp&nbsp&nbsp K₂ = 6.2 x 10^-8

HPO₄^2- <--> H⁺ + PO₄^3- &nbsp&nbsp&nbsp&nbsp K₃ = 3.6 x 10^-13