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

Answer 1

The Correct Option is A

To solve the given question, we will examine both the assertion and the reason provided.

1. Understanding the Ellingham Diagram:
   • An Ellingham diagram is a graph showing the temperature dependence of the stability of compounds. It is mainly used to determine the reduction of metal oxides. On this diagram, the ΔG (Gibbs free energy change) is plotted against temperature.
   • In the Ellingham diagram, the oxidation of carbon to carbon monoxide (C + \frac{1}{2}O_2 \rightarrow CO) shows a negative slope with respect to temperature.
   • The negative slope is due to the fact that the reaction involves an increase in entropy, as gas molecules are formed during the reaction.
2. Analyzing the Assertion (A):
   • The assertion states that the oxidation of carbon to carbon monoxide shows a negative slope with respect to temperature in an Ellingham diagram.
   • This is correct because, as explained above, the entropic gain in the reaction causes the slope to become negative in the temperature range studied in Ellingham diagrams.
3. Analyzing the Reason (R):
   • The reason provided is that carbon monoxide (CO) tends to decompose at higher temperatures.
   • This is also correct because, at higher temperatures, the decomposition of CO to C and CO₂ becomes favorable, which aligns with the behavior seen on the Ellingham diagram.
4. Evaluating the Relationship:
   • Both the assertion and reason are correct statements. However, the negative slope due to entropy changes is fundamentally related to the nature of the reaction shown in the Ellingham diagram, where the decomposition stability of CO at higher temperatures essentially supports this behavior.
   • Therefore, the reason correctly explains why the assertion is true, as the decomposition tendency of CO at higher temperatures aligns with the slope change.

In conclusion, both the assertion (A) and reason (R) are correct, and R is indeed the correct explanation of A. Therefore, the correct answer is: Both A and R are correct, and R is the correct explanation of A.