Cr2VIO72- + 14 H+ + 12 (I-I)- 2 Cr0 + 6 I20 + 7 H2O

This is an oxidation-reduction (redox) reaction:

12 I-I - 12 e- 12 I0 (oxidation)

2 CrVI + 12 e- 2 Cr0 (reduction)

Change the oxidation states