Hydrogen phosphate ion (HPO₄²⁻)
- Charge
- −2
- Atoms
- H, P, O × 4
- Atoms in total
- 6
- Mass of the ion
- 95.978 g/mol
Hydrogen phosphate is one hydrogen, one phosphorus and four oxygen atoms with a 2− charge. It forms when phosphoric acid, H₃PO₄, loses two of its three hydrogen ions, or when phosphate, PO₄³⁻, picks up one. You meet it in fertilizers, in processed cheese and as one half of the buffer that keeps your cells close to neutral pH.
- Its full name is monohydrogen phosphate, and its salts are often named with di-, as in disodium phosphate, Na₂HPO₄.
- Adding H⁺ one at a time makes the charge less negative: PO₄³⁻, then HPO₄²⁻, then H₂PO₄⁻.
- Diammonium phosphate, (NH₄)₂HPO₄, is one of the most widely used fertilizers in the world.
Compounds that contain hydrogen phosphate
Na2HPO4 Disodium hydrogen phosphate
K2HPO4 Dipotassium hydrogen phosphate
(NH4)2HPO4 Diammonium hydrogen phosphate
CaHPO4 Calcium hydrogen phosphate