Question

Why Zinc oxide can be reduced to metal by heating with carbon but chromium oxide cannot be reduced by heating with carbon

Answer 1

Oxides of moderately reactive metals such as zinc can be reduced by carbon because carbon has more affinity for oxygen than zinc due to which zinc oxide is reduced to zinc metal and carbon combines with oxygen to form carbon monoxide.
Whereas, oxides of reactive metals such as chromium cannot be reduced by using carbon because carbon has less affinity for oxygen than chromium due to which chromium oxide is not reduced to chromium metal.