10 HClVIIO4 + 18 HI-I + 2 K2Cr2VIO7 2 Cr2135/10(Cl-IO4)3 + 4 KClVIIO4 + 9 I20 + 14 H2O

This is an oxidation-reduction (redox) reaction:

6 ClVII + 48 e- 6 Cl-I (reduction)

18 I-I - 18 e- 18 I0 (oxidation)

4 CrVI - 30 e- 4 Cr135/10 (oxidation)

Change the oxidation states