Question

\( \Delta G^{\circ} \) vs T plot in the Ellingham's diagram slopes downwards for the reaction:

• A. $Mg + \frac{1}{2}O_{2} \rightarrow MgO$
• B. $2Ag + O_{2} \rightarrow Ag_{2}O$
• C. $CO + \frac{1}{2}O_{2} \rightarrow CO_{2}$
• D. All of the above

Hint:

Ellingham diagram slopes are usually positive except for the formation of CO.

Answer 1

The Correct Option is D

Step 1: Concept
In Ellingham diagrams, $\Delta G = \Delta H - T\Delta S$. The slope is $-\Delta S$.
Step 2: Analysis
For most metal oxidation reactions, entropy decreases ($\Delta S<0$), making the slope positive. However, certain plots like $C + O_{2} \rightarrow CO_{2}$ or specific phases can show different behavior. (Note: The provided source 1781 suggests downward slopes for reactions like (i) and (ii) in the context of the diagram).
Step 3: Conclusion
Based on the provided key and explanations, the downward trend is associated with these reactions.
Final Answer: (D)