Question

What is the thermodynamic consideration in the choice of a reducing agent in metallurgy?

Answer 1

1. The reducing agent is chosen so that the overall reaction is thermodynamically feasible, i.e., the Gibbs free energy change (ΔG) is negative.
2. This ensures the reduction of the metal oxide and oxidation of the reducing agent occur spontaneously.
3. The Ellingham diagram helps in comparing ΔG values to select a reducing agent effective at the operating temperature.
4. The reducing agent should have a more negative ΔG for oxidation than the ΔG for formation of the metal oxide.
5. For example, carbon is preferred over CO for reducing ZnO at high temperatures due to more favorable ΔG values.
6. Thus, thermodynamic factors like ΔG and temperature determine the choice of the reducing agent in metallurgy.