Question

Given below are two statements.
Statement I : The choice of reducing agents for metals extraction can be made by using Ellingham diagram, a plot of \(\Delta G\) vs temperature.
Statement II : The value of \(\Delta S\) increases from left to right in Ellingham diagram.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

In Ellingham diagrams, the slope is \(-\Delta S\). A sudden change in slope indicates a phase transition (melting or boiling) of one of the reactants or products.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ellingham diagrams provide a graphical representation of the change in Gibbs free energy with temperature for the formation of oxides. They are used to determine the temperature range and reducing agent suitable for metal extraction.
Step 2: Detailed Explanation:
1. Analysis of Statement I: The Ellingham diagram plots \(\Delta G_f^\circ\) vs \(T\). A metal can reduce the oxide of another metal if its line is below the other's line at a given temperature. Thus, it helps in choosing the right reducing agent. Statement I is true.
2. Analysis of Statement II: The equation for the lines is \(\Delta G = \Delta H - T\Delta S\). The slope of the line is \(-\Delta S\). For most metal oxidation reactions (\(2M + O_2 \to 2MO\)), \(\Delta S\) is negative because gaseous oxygen is consumed. Consequently, the slope \(-\Delta S\) is positive, and the lines go upwards. The value of \(\Delta S\) for a given reaction remains relatively constant unless a phase change occurs; it does not "increase from left to right" as a general rule across the temperature axis. Statement II is false.
Step 3: Final Answer:
Statement I is true but Statement II is false.