8 HClVIIO4 + 22 HI-I + K2Cr2VIO7 2 CrIII(ClVIIO4)3 + 11 I20 + 2 KCl-I + 15 H2O

This is an oxidation-reduction (redox) reaction:

2 ClVII + 16 e- 2 Cl-I (reduction)

22 I-I - 22 e- 22 I0 (oxidation)

2 CrVI + 6 e- 2 CrIII (reduction)

Change the oxidation states