Mn{+2} + KIO4 --> MnO4 + *what?*

Question

In class we were tasked with writing a balanced reaction for when Mn²⁺ reacts with KIO₄ to form MnO₄^-. However, we were only told the resulting substance from the oxidation part of the redox reaction, that MnO₄^- is formed, not the reduction, i.e. what is formed from the iodine. Apparently the IO₄^- turns into IO₃^- but how can we know that's what will happen if we haven't been given that information beforehand? How do we know how many oxygen will be in the resulting ion? How do we know it'll become IO₃^- and not IO₂^- or IO or just KI like 3e^- + Mn²⁺ + KIO --> MnO₄^- + KI or something like that?

Answer 1

You choose the first step in the process, in this case, IO4- ==> IO3-.

So, the iodine will be reduced from 7+ to 5+ before being further reduced to 3+ and 1+.