The Δf G° of CO2 from CO is always higher reduction of ZnO to Zn. In contrast, Δf G° of CO from C is lower at temperature above 1180K while that of CO2 from C is lower at temperatures above 1270K than Δf G° of ZnO. Thus above 1270K, ZnO can be reduced to Zn by C. In actual practice, reduction is usually carried out around 1673K. Thus out of C and CO, C is a better reducing agent than CO for ZnO.
