FeIIS2-I + 8 HNVO3 FeIII(NVO3)3 + 5 NIIO + 2 H2SVIO4 + 2 H2O

This is an oxidation-reduction (redox) reaction:

2 S-I - 14 e- 2 SVI (oxidation)

5 NV + 15 e- 5 NII (reduction)

FeII - 1 e- FeIII (oxidation)

Change the oxidation states