4 FeIICu2IS2-II + 15 O20 2 Fe2IIIO3-II + 8 CuIIO-II + 8 SIVO2-II

This is an oxidation-reduction (redox) reaction:

8 CuI - 8 e- 8 CuII (oxidation)

8 S-II - 48 e- 8 SIV (oxidation)

4 FeII - 4 e- 4 FeIII (oxidation)

30 O0 + 60 e- 30 O-II (reduction)

Change the oxidation states