KCET · Chemistry · General Principles and Processes of Isolation of Metals

From the Ellingham graphs on carbon, which of the following statements is false?

A \(\mathrm{CO}\) reduces \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) to \(\mathrm{Fe}\) at less than \(983 \mathrm{~K}\)
B \(\mathrm{CO}\) is less stable than \(\mathrm{CO}_{2}\) at more than \(983 \mathrm{~K}\)
C \(\mathrm{CO}\) reduces \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) to \(\mathrm{Fe}\) in the reduction zone of blast furnace
D \(\mathrm{CO}_{2}\) is more stable than \(\mathrm{CO}\) at less than \(983 \mathrm{~K}\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(\mathrm{CO}\) is less stable than \(\mathrm{CO}_{2}\) at more than \(983 \mathrm{~K}\)

Step-by-step Solution

Detailed explanation

In Ellingham graph, initially the \(\Delta_{\mathrm{f}} \mathrm{G}^{\circ}\) more negative for \(\mathrm{CO}_{2}\), thus, \(\mathrm{CO}_{2}\) is more stable than CO but when the temperature becomes \(983 \mathrm{~K}\), the conditions inverted i.e., \(\Delta_{f} \mathrm{G}^{\circ}\) of \(\mathrm{CO}\) becomes more negative and hence above \(983 \mathrm{~K}\), CO becomes more stable than \(\mathrm{CO}_{2}\).

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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