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Amphoteric Species

Submitted by jpthehp on Tue, 04/13/2010 - 22:44

of the following which one/s are amphoteric species
NH4(+)  HBO3(2-)  H2PO4(-)
I know amphoteric species can serve as either acids or
bases but do not know how to determine if one is amphoteric
when given a list that probable sounds dumb any help would
be appreciated, thanks


NH4+ can behave as an acid  ---> NH3  + H+  (but is not a base, so is not amphoteric)

The other two ions can either lose protons (acids) or add protons (behave a bases)

eg

  H2PO4-  +  H2O  HPO42-    +    H3O+
  acid          base            conj base        conj acid

or
  H2PO4-  +  H3O+  H3PO4    +    H2O
  base          acid            conj acid      conj base