3 Hg2II2-I + 14 HNVO3 + 12 HCl 6 HgIICl2 + 6 HIVO3 + 14 NIIO + 10 H2O

This is an oxidation-reduction (redox) reaction:

6 I-I - 36 e- 6 IV (oxidation)

14 NV + 42 e- 14 NII (reduction)

6 HgI - 6 e- 6 HgII (oxidation)

Change the oxidation states