Chapter 15, Problem 5PE

Which of the following are amphoteric and which are not? Provide reasons for your decisions: (a) ${\text{ H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}\text{,}$ (b) ${\text{H}}_{\text{2}}\text{S}\left(I\right),$ (c) ${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}\text{,}$ (d) $N{H}_4{}^{+},$ (e) ${\text{H}}_{\text{2}}\text{O,}$ (f) HI. (g) ${\text{HNO}}_{\text{2}}\text{.}$ (Hint: Amphoteric substances must be able to provide an ${\text{H}}^{\text{+}}$ and also react with an ${\text{H}}^{\text{+}}$.)