C2-IIH4 + 6 Cl20 2 CIVCl4-I + 4 HCl-I

This is an oxidation-reduction (redox) reaction:

2 C-II - 12 e- 2 CIV (oxidation)

12 Cl0 + 12 e- 12 Cl-I (reduction)

Change the oxidation states