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GATE 2025 MT – Question 30

Metallurgical Thermodynamics · Reaction equilibria and Ellingham diagrams · 1 mark · Multiple select

Standard Gibbs free energies of formation of solid oxides per mole of O$_2$ at 1000 K are: SiO$_2$: −728 kJ; TiO$_2$: −737 kJ; VO: −712 kJ; MnO: −624 kJ. Regarding thermodynamic feasibility of oxide reduction, which statements are correct under standard conditions at 1000 K?

  1. Si can reduce TiO2.
  2. Mn can reduce VO.
  3. Ti can reduce MnO.
  4. V can reduce SiO2.

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Correct answer: (C) Ti can reduce MnO.

Explanation

For oxygen transfer under standard conditions, the reducing metal must form the more stable oxide, with more negative formation Gibbs energy on the same O2 basis. TiO2 at −737 kJ is more stable than MnO at −624 kJ, so Ti reduces MnO. Each other proposed reducing oxide is less stable than the oxide attacked. **C**.