3 C2-IH4O + Cr2VIO72- + 8 H+ 3 C20H4O2 + 2 (CrIII)3+ + 4 H2O

This is an oxidation-reduction (redox) reaction:

6 C-I - 6 e- 6 C0 (oxidation)

2 CrVI + 6 e- 2 CrIII (reduction)

Change the oxidation states