An amphiprotic substance is a substance that can donate or accept a proton, H+

For a substance to be amphiprotic it must

  1. contain a hydrogen atom which is able to be donated to another chemical species.
  2. be able to accept a hydrogen ion from another species.

Examples of amphiprotic species include, H2O, HCO3- , HSO4- , HPO42- and H2PO4-

Name of amphiprotic species Chemical formula Able to donate a proton, H+ Able to accept a proton, H+
Water H2O H2O(l) → H+(aq) + OH-(aq) H2O(l) + H+(aq) → H3O+(aq)
Hydrogen carbonate ion HCO3- HCO3-(aq) → H+(aq) + CO32-(aq)  HCO3-(aq) + H+(aq) → H2CO3(aq)
Hydrogen sulfate ion HSO4- HSO4-(aq) → H+(aq) + SO42-(aq) HSO4-(aq) + H+(aq) → H2SO4(aq)
Dihydrogen phosphate ion H2PO4- H2PO4-(aq) → H+(aq) + HPO42-(aq) H2PO4-(aq) + H+(aq) → H3PO4(aq)

 Amphiprotic substances are a subset of amphoteric species since they can act as an acid or a base.



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