6 HINVO3 + I20 2 H20 + 2 HIIVO3 + 6 NIVO2

This is an oxidation-reduction (redox) reaction:

4 HI + 4 e- 4 H0 (reduction)

2 I0 - 10 e- 2 IV (oxidation)

6 NV + 6 e- 6 NIV (reduction)

Change the oxidation states