Following method of extracting Zn is based on thermodynamics
A : 2ZnS+3O2⟶2ZnO+2SO2
B : ZnO+C⟶Zn+CO
If △Gof (standard free energies of formation, in kJmol−1 ) of ZnS=−205.4, ZnO=−318.0, SO2=−300.4 and of CO=−137.3
Free energy changes of the above reaction A and B (respectively) will be :