Cr2VIO72- + 6 (FeII)2+ + 14 H+ 2 (CrIII)3+ + 6 (FeIII)3+ + 7 H2O

This is an oxidation-reduction (redox) reaction:

2 CrVI + 6 e- 2 CrIII (reduction)

6 FeII - 6 e- 6 FeIII (oxidation)

Change the oxidation states