[jalen]

I₃^- ---> I^- + IO₃^-
I₃^- + H₂O ----> IO₃^-
I₃^- + H₂O ----> 3IO₃^-
I₃^- + 9H₂O ----> 3IO₃^-
I₃^- + 9H₂O ----> 3IO₃^- + 18H⁺
I₃^- + 9H₂O ----> 3IO₃^- + 18H⁺ + 6e^-

I^- ---> I₃^-
I^- + 1e^- ---> I₃^- (x6)
6I^- + 6e^----> 6I₃^-

I₃^- + 9H₂O + 6I^----> 3IO₃^- + 18H⁺ + 6I₃^-

Where did I go wrong?? Can't seem to find my mistake.
 

[boostar]

I'm not saying I know the answer and I may be making a fool out of myself but I'll give it a shot:

I3- ---> I- + IO3-
I3- + H2O ----> IO3-... consider the charge on I, remembering that the overall compound is -1
I3- + H2O ----> 3IO3-
I3- + 9H2O ----> 3IO3-
I3- + 9H2O ----> 3IO3- + 18H+
I3- + 9H2O ----> 3IO3- + 18H+ + 6e-

I- ---> I3-
I- + 1e- ---> I3- (x6)
6I- + 6e----> 6I3-... this definitely is not balanced. Rethink the charges on both Iodines in the equation.

Sorry I did not use the sup and sub scripts but it just got very confusing :p

[Borek]

I^- ---> I₃^-

Quite the reverse.