`FeS_2 + O_2 -> Fe_2O_3 + SO_2`
Oxidation number it is the number assigned to a compound which represent the number of electrons lost or gained.
FeS2 = Fe(+2); S(-2)
Here it has to be Fe+2 and S-1 but here it is persulphide rather than disulphide. So S will have -2 derived from H2S2
O2 = 0
The oxidation number of an element in its elemental state is 0.
Oxygen atom will have -2 oxidation state and in peroxide it will have -1 oxidation state and in superoxide it will have -1/2.... But O2 has 0 oxidation number like H2 and N2 also have 0 oxidation state.
Fe2O3 = Fe(+3); O(-2)
SO2 = S(+4); O(-2)
Following is the list of oxidation numbers for all the species: Fe in FeS2= +2, i.e. ferrous state; S2 (2-) in FeS2 = -2, it is called persulfide ion, here each S has an oxidation number of -1; O in O2 has an oxidation number of 0, as every element in free state has oxidation number zero; Fe in Fe2O3 = +3, i.e. ferric state; O in Fe2O3 = -2, i.e. oxide ion; S in SO2 has an oxidation number of +4; O in SO2 = -2. Hope this information will be of some help!
FeS2+ O2 ------> Fe2O3 + SO2
In terms of the oxidation numbers, we can write this equation:
Fe (+ 2) – 1e ------>Fe +3
S2 (–1) – 10e --------> 2S +4
O2 (0) + 4e ---------->2O –2
The oxidation state of FeS2 = +2 and S2(-2)
O2 the oxidation state of oxygen is zero. Fe in Fe2O3 = +3 S in SO2 has an oxidation number of +4. In SO2 the oxidation state of oxygen is -2.