Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: In an Ellingham diagram, the oxidation of carbon to carbon monoxide shows a negative slope with respect to temperature
Reason R: CO tends to get decomposed at higher temperature
In the light of the above statements, choose the correct answer from the options given below

• A. A is correct but $R$ is not correct
• B. $A$ is not correct but $R$ is correct
• C. Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$
• D. Both $A$ and $R$ are correct but $R$ is NOT the correct explanation of $A$

Hint:

In an Ellingham diagram, a negative slope indicates that the reaction becomes more favorable at higher temperatures, while a positive slope indicates that the reaction becomes less favorable.

Answer 1

The Correct Option is A

The given question consists of an Assertion (A) and a Reason (R), and we need to identify the correct relationship between them based on the options provided.

Assertion A: In an Ellingham diagram, the oxidation of carbon to carbon monoxide shows a negative slope with respect to temperature.

Reason R: CO tends to get decomposed at higher temperature.

Let us evaluate each statement:

1. Assertion (A) Analysis:
   • An Ellingham diagram represents the change in Gibbs free energy (ΔG) for the formation of oxides at different temperatures. It is typically used to compare the thermodynamic stability of various oxides.
   • The slope of a line in the Ellingham diagram is related to the entropy change (ΔS) for the reaction. The oxidation reaction C + 1/2 O_2 → CO shows a negative slope. This occurs because (for gases) as temperature increases, ΔG becomes less positive (or more negative, thus a downward slope) due to a positive ΔS.
   • Since this is a characteristic feature of the reaction of carbon to carbon monoxide, the assertion (A) is correct.
2. Reason (R) Analysis:
   • The reason states that CO tends to get decomposed at higher temperatures, which implies CO is unstable at high temperatures.
   • While it is true that CO can indeed decompose at higher temperatures under certain conditions, this is not the reason for the negative slope. Therefore, Reason (R) is not a correct explanation for Assertion (A).

Based on this analysis, we can conclude:

• The assertion (A) is correct as it properly describes the behavior of carbon oxidation in an Ellingham diagram.
• Reason (R), even if partially correct under separate circumstances, does not explain the negative slope in the Ellingham diagram related to this reaction.

Therefore, the correct answer is: A is correct but R is not correct.