Question

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`

Answer 1

The one whose oxidation number decreases during the redox process is the oxidizing agent.

Explanation:

`2MnO_4^(-) + 5H_2SO_3 rarr Mn^(2+) +5SO_4^(2-) +4H^(+) + 3H_2O`

Sulfite (`SO_3^(2-), S(IV)`) is oxidized to sulfate (`SO_4^(2-), S(VI)`), and this sulfite serves as the reducing agent.

Manganese (as permanganate) is reduced to the almost colourless `Mn^(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.