C2-IIH5OH + 4 I20 + NaOH CIIHI3-I + HCIIOONa + 5 HI-I

This is an oxidation-reduction (redox) reaction:

2 C-II - 8 e- 2 CII (oxidation)

8 I0 + 8 e- 8 I-I (reduction)

Change the oxidation states