4 FeS2-I + 9 O20 2 Fe2SIIO3-II + 6 SIVO2-II

This is an oxidation-reduction (redox) reaction:

2 S-I - 6 e- 2 SII (oxidation)

6 S-I - 30 e- 6 SIV (oxidation)

18 O0 + 36 e- 18 O-II (reduction)

Change the oxidation states