N2-IIH4I + O20 2 H20 + 2 NIIO-II

This is an oxidation-reduction (redox) reaction:

4 HI + 4 e- 4 H0 (reduction)

2 N-II - 8 e- 2 NII (oxidation)

2 O0 + 4 e- 2 O-II (reduction)

Change the oxidation states