I20 + 4 Cl20 + 6 H2O 2 IIVO32- + 8 (Cl-I)- + 12 H+

This is an oxidation-reduction (redox) reaction:

2 I0 - 8 e- 2 IIV (oxidation)

8 Cl0 + 8 e- 8 Cl-I (reduction)

I2 is a reducing agent, Cl2 is an oxidizing agent.