Aqueous solution of `H_(2)S` contains `H_(2)S, HS^(-),S^(2-),H_(3)O^(+),OH^(-)` and `H_(2)O` in varying concentrations. Which of these species can act only as a base? Which can act only as an acid? Which can act both as an acid and as a base?

Explanation

`to H_(2)S, H_(3)O^(+)` acts as only acids
`to HS^(-),OH^(-), H_(2)O` acts as acids as well as bases
`to S^(-2)` acts as only base