3 C2-IIH6O + 8 H3O+ + Cr2VIO72- 3 C2-IH4O + 2 (CrIII)3+ + 15 H2O

This is an oxidation-reduction (redox) reaction:

6 C-II - 6 e- 6 C-I (oxidation)

2 CrVI + 6 e- 2 CrIII (reduction)

Change the oxidation states