2 FeIIS2-I + 14 HINVO3 2 FeIII(NVO3)3 + 3 H20 + 8 NIIO + 4 H2ISVIO4

This is an oxidation-reduction (redox) reaction:

4 S-I - 28 e- 4 SVI (oxidation)

6 HI + 6 e- 6 H0 (reduction)

8 NV + 24 e- 8 NII (reduction)

2 FeII - 2 e- 2 FeIII (oxidation)

Change the oxidation states