Reaction (a) i.e 2Cu2S+3O2→2Cu2O+2SO2 copper extraction via roasting. Reaction (b) i.e 2FeS+3O2→2FeO+2SO2 is use to remove iron oxide from copper ore. Reaction (c) i.e FeO+SiO2→FeSiO3 is removal of slag in copper extraction. SiO2+CaO→CaSiO3 is not related to copper extraction.
