The chief ore of Zn is the sulphide, ZnS. The ore is concentrated by froth floatation process and then heated in air to convert ZnS to ZnO.
2ZnS+3O280%−−→2ZnO+2SO2
ZnO+H2SO4100%−−−→ZnSO4+H2O
2ZnSO4+2H2O80%−−→2Zn+2H2SO4+O2
The number of moles of ZnS required to produce 2 moles of Zn will be: