Answer
Acting like an Acid:
$H{SO_3}^-(aq) + H_2O(l) --> S{O_3}^{2-}(aq) + H_3O^+(aq)$
Acting like a Base:
$H{SO_3}^-(aq) + H_2O(l) --> H_2{SO_3}(aq) + OH^{-}(aq)$
Work Step by Step
When the ion acts like an Acid, it gives one proton to water:
$H{SO_3}^-(aq) + H_2O(l) --> {SO_3}^{2-}(aq) + H_3O^+(aq)$
When the ion acts like a Base, it receives one proton from water:
$H{SO_3}^-(aq) + H_2O(l) --> H_2{SO_3}(aq) + OH^{-}(aq)$
