Question

What are thermodynamic principles of metallurgy? Explain with a suitable example.

Answer 1

1. A chemical reaction in metallurgy occurs spontaneously if ΔG is negative.
2. ΔG is calculated by the formula: ΔG = ΔH − TΔS, where ΔH is enthalpy change, T is temperature, and ΔS is entropy change.
3. The reducing agent is chosen such that the overall reaction has a negative ΔG.
4. For example, in the reduction of iron oxide (FeO) by carbon:
   • \[\ce{FeO + C -> Fe + CO}\]
   • This reaction occurs only if the combined ΔG for FeO reduction and C oxidation is negative.
5. The Ellingham diagram helps to determine the temperature at which a reducing agent can reduce a metal oxide.
6. At temperatures above 1073 K, carbon effectively reduces FeO to Fe because ΔG becomes negative.

Thus, thermodynamic principles help predict and control metal extraction processes by ensuring reactions are spontaneous under given conditions.