Monohydrogen phosphate

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Monohydrogen phosphate
Hydrogen phosphate.svg
Identifiers
  • 14066-19-4
3D model (JSmol)
ChEBI
ChemSpider
1998
UNII
  • InChI=1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)/p-2
    Key: NBIIXXVUZAFLBC-UHFFFAOYSA-L
  • OP(=O)([O-])[O-]
Properties
HO4P−2
Molar mass 95.979 g·mol−1
Related compounds
Related compounds
 , Phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Monohydrogen phosphate is the inorganic ion with the formula [HPO4]2-. Its formula can also be written as [PO3(OH)]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.[1] 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:

Equilibrium Disassociation constant, pKa[2]
H3PO4 ⇌ H
2PO−
4 + H+ 		pKa1 = 2.14[a]
H
2PO−
4 ⇌ HPO2−
4 + H+ 		pKa2 = 7.20
HPO2−
4 ⇌ PO3−
4 + H+ 		pKa3 = 12.37
  1. ^ Values are at 25 °C and 0 ionic strength.

Examples[]

References[]

  1. ^ Schrödter, Klaus; Bettermann, Gerhard; Staffel, Thomas; Wahl, Friedrich; Klein, Thomas; Hofmann, Thomas (2008). "Phosphoric Acid and Phosphates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3.
  2. ^ Powell, Kipton J.; Brown, Paul L.; Byrne, Robert H.; Gajda, Tamás; Hefter, Glenn; Sjöberg, Staffan; Wanner, Hans (2005). "Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg2+, Cl−, OH−, CO2−
    3    , SO2−
    4    , and PO3−
    4     aqueous systems"    . Pure Appl. Chem. 77 (4): 739–800. doi:10.1351/pac200577040739.
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