JEE Main · 2023 · 10 Apr 2023 · Shift 2 · Chemical Thermodynamics

On an Ellingham diagram a reducing agent can reduce an oxide only when its own oxidation line lies below that oxide's line at the chosen temperature. At $600^{\circ }\mathrm{C}$ the $\mathrm{C}\to \mathrm{C}{\mathrm{O}}_2$ line lies below the $\mathrm{Fe}\to \mathrm{FeO}$ line, while the $\mathrm{ZnO}$ line lies well below the carbon line and the $\mathrm{CO}$ line lies above the $\mathrm{ZnO}$ line. So carbon cannot reduce $\mathrm{ZnO}$ and CO cannot reduce $\mathrm{ZnO}$ at this temperature, but carbon can reduce $\mathrm{FeO}$ to iron.