Dihydrogen phosphate


Dihydrogen phosphate is an inorganic ion with the formula −. Phosphates occur widely in natural systems. Perhaps the most common salt of dihydrogen phosphate is sodium dihydrogen phosphate. It is used in animal feed, fertilizer, buffer, and treating metal surfaces.

Structure

The dihydrogen phosphate anion consists of a central phosphorus atom bonded two oxides and two hydroxy groups in a tetrahedral arrangement.

Acid-base equilibria

Dihydrogen phosphate can be both a hydrogen donor and acceptor.
EquilibriumDisassociation constant, pKa
H3PO4 + H+pKa1 = 2.14
+ H+pKa2 = 7.20
+ H+pKa3 = 12.37

Examples

Safety

Many foods including milk, eggs, poultry, and nuts contain these sodium phosphates.