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Above what temperature does carbon-based reduction of metal oxide M'O occur, producing metal M' and the acidic oxide of carbon (CO2)?
- 2100 K
- 2550 K
- 1300 K
- 600 K
Correct answer: 1300 K
Solution
On the Ellingham diagram, the free energy line for C + O2 -> CO2 is relatively flat. For ZnO (a common M'O in JEE problems), carbon reduction to give CO2 becomes spontaneous above approximately 1300 K, which is the intersection point where Delta-G for the overall reaction becomes negative.
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