7 P40 + 12 NaOH + 24 H2O 12 NaHPIVO3 + 16 P-IIIH3

This is an oxidation-reduction (redox) reaction:

16 P0 + 48 e- 16 P-III (reduction)

12 P0 - 48 e- 12 PIV (oxidation)

Change the oxidation states