Everything about Phosphates totally explained
Phosphate, in
inorganic chemistry, is a
salt of
phosphoric acid. Inorganic phosphates are
mined to obtain
phosphorus for use in industry.
In
organic chemistry, a phosphate, or
organophosphate, is an
ester of phosphoric acid. Organic phosphates are important in
biochemistry and
biogeochemistry.
Chemical properties
polyatomic ion with the
empirical formula PO43− and a
molar mass of 94.973 g/mol; it consists of one central
phosphorus atom surrounded by four identical oxygen atoms in a
tetrahedral arrangement. The phosphate ion carries a negative three formal charge and is the
conjugate base of the hydrogenphosphate ion, H
PO
42−, which is the conjugate base of H
2PO
4−, the dihydrogen phosphate ion, which in turn is the conjugate base of H
3PO
4,
phosphoric acid. It is a
hypervalent molecule (the phosphorus atom has 10 electrons in its
valence shell). Phosphate is also an
organophosphorus compound with the formula OP(OR)
3
A phosphate salt forms when a positively-charged ion attaches to the negatively-charged oxygen atoms of the ion, forming an ionic
compound. Many phosphates are not
soluble in
water at
standard temperature and pressure.
In dilute aqueous solution, phosphate exists in four forms. In strongly-basic conditions, the phosphate ion (PO
43−) predominates, whereas in weakly-basic conditions, the hydrogen phosphate ion (HPO
42−) is prevalent. In weakly-acid conditions, the dihydrogen phosphate ion (H
2PO
4−) is most common. In strongly-acid conditions, aqueous phosphoric acid (H
3PO
4) is the main form.
Image:3-phosphoric-acid-3D-balls.png|H3PO4
Image:2-dihydrogenphosphate-3D-balls.png|H2PO4−
Image:1-hydrogenphosphate-3D-balls.png|HPO42−
Image:0-phosphate-3D-balls.png|PO43−
More precisely, considering the following three equilibrium reactions:
» H
3PO
4 ⇌ H
+ + H2PO4−
» H2PO4− ⇌ H+ + HPO42−
» HPO42− ⇌ H+ + PO43−
the corresponding constants at 25°C (in mol/L) are (see phosphoric acid):
»
showing that H3PO4 is dominant with respect to H2PO4−. HPO42− and PO43− are practically absent.
Phosphate can form many polymeric ions such as diphosphate (also pyrophosphate), P2O74−, and triphosphate, P3O105−. The various metaphosphate ions have an empirical formula of PO3− and are found in many compounds.
Phosphate deposits can contain significant amounts of naturally occurring uranium. Uptake of these substances by plants can lead to high uranium concentrations in crops.
Cellular function
Phosphate is useful in animal cells as a buffering agent. The kinds of phosphate that are useful as buffers include NaH2PO4- and H2PO4-.
Further Information
Get more info on 'Phosphates'.
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