Answer
(a) Acids: $HOBr$ and $H_3O^+$; Bases: $OBr^-$ and $H_2O$.
(b) Acids: $H{SO_4}^-$ and $H_3O^+$; Bases: ${SO_4}^{2-}$ and $H_2O$.
(c) Acids: $H_2S$ and $H_2O$; Bases: $HS^-$ and $OH^-$.
(d) Acids: $C_6H_5{NH_3}^+$ and $H_2O$; Bases: $C_6H_5NH_2$ and $OH^-$.
Work Step by Step
Identify the compounds that are losing a proton during the reaction, these are the acids.
The compounds that are gaining a proton during the reaction are the bases.
** Remember to analyze both forward and reverse reactions, like, the $H_3O^+$ is donating a proton in (a) reverse reaction.
