how much does the oxidation number of iodine increase?

Question

how much does the oxidation number of iodine increase in the reaction:

2MnO4– + I– + H2O -----> 2MnO2 + IO3– + 2OH–

is it 6?

Answer 1

Yes. In I-, the oxidation number is -1. In IO3-, the oxidation number is +5. Iodine is being oxidized from the -1 state to the +5 state, a change of +6.

As an aside, each Mn atom is being reduced from a +7 state to a +4 state. Each of the two Mn atoms is being reduced by 3 in oxidation number...in a sense this "adds up" to -6.