# How do you identify the oxidizing agent in the following chemical reaction? 2MnO_4^- + 5H_2SO_3 -> 2Mn^(+2) + 5SO_4^(-2) + 4H^+ + 3H_2O

$2 M n {O}_{4}^{-} + 5 {H}_{2} S {O}_{3} \rightarrow M {n}^{2 +} + 5 S {O}_{4}^{2 -} + 4 {H}^{+} + 3 {H}_{2} O$
Sulfite ($S {O}_{3}^{2 -} , S \left(I V\right)$) is oxidized to sulfate ($S {O}_{4}^{2 -} , S \left(V I\right)$), and this sulfite serves as the reducing agent.
Manganese (as permanganate) is reduced to the almost colourless $M {n}^{2 +}$, so what you would see here is the reaction mix losing its deep purple colour at the endpoint. Because of this colour change, this redox reaction is self-indicating. And this permanganate ion, which features high oxidation state manganese, is the oxidizing agent here.