2 P0 + 4 NaOHI + 2 H2IO 2 Na2HIPIIIO3 + 3 H20

This is an oxidation-reduction (redox) reaction:

2 P0 - 6 e- 2 PIII (oxidation)

6 HI + 6 e- 6 H0 (reduction)

Change the oxidation states