Answer:
[tex]HCO_{3}^{-}[/tex]
Explanation:
Chemical species which can behave as both acids and bases are known as amphoteric species.
[tex]HCO_{3}^{-}[/tex] can behave as both acid and base.
[tex]HCO_{3}^{-}[/tex] can donate H+:
[tex]HCO_3^{-} \rightarrow CO_3^{2-} + H^+[/tex]
[tex]HCO_{3}^{-}[/tex] can accept H+ as well:
[tex]HCO_3^{-} + H^+ \rightarrow H_2CO_3[/tex]
HF can only behave as acid, as it can only donate H+.
[tex]HF(aq) \rightarrow H^{+}(aq) + F^{-}(aq)[/tex]
[tex]NH_4^{+}[/tex] is a conjugate acid of [tex]NH_3[/tex].
[tex]PO_4^{2-}[/tex] is a conjugate base.
