Monohydrogen phosphate


Monohydrogen phosphate is the inorganic ion with the formula 2-. Its formula can also be written as 2-, which shows the presence of a O-H bond. Together with dihydrogen phosphate, monohydrogen phosphate occurs widely in natural systems. Their salts are used in fertilizers and in cooking. Most monohydrogenphosphate salts are colorless, water soluble, and nontoxic.

Acid-base equilibria

Monohydrogenphosphate is an intermediate in the multistep conversion of phosphoric acid to phosphate:
EquilibriumDisassociation constant, pKa
H3PO4 + H+pKa1 = 2.14
+ H+pKa2 = 7.20
+ H+pKa3 = 12.37

Examples