2 HIVO3 + 10 FeIISO4 + 5 H2SO4 I20 + 5 Fe2III(SO4)3 + 6 H2O

This is an oxidation-reduction (redox) reaction:

2 IV + 10 e- 2 I0 (reduction)

10 FeII - 10 e- 10 FeIII (oxidation)

Change the oxidation states