5 I20 + Cl20 + 6 H2O 2 HClVO3 + 10 HI-I

This is an oxidation-reduction (redox) reaction:

10 I0 + 10 e- 10 I-I (reduction)

2 Cl0 - 10 e- 2 ClV (oxidation)

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