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

To determine the most appropriate answer to the given statements regarding the Ellingham diagram, let's analyze each statement:

1. Statement I: "The choice of reducing agents for metals extraction can be made by using Ellingham diagram, a plot of \( \Delta G \) vs temperature."
   • The Ellingham diagram is a graph that plots the Gibbs free energy change \( \Delta G \) against temperature for the formation of oxides of various elements. It helps in determining which reducing agent can reduce a particular metal oxide by observing the relative positions of the lines in the diagram.
   • If the line for a particular metal is lower than that of a reducing agent, it means that the reducing agent can effectively reduce the metal oxide to the metal.
   • Since the Ellingham diagram indeed assists in selecting reducing agents based on thermodynamic feasibility, Statement I is true.
2. Statement II: "The value of \( \Delta S \) increases from left to right in Ellingham diagram."
   • The slope of the lines in the Ellingham diagram corresponds to the change in entropy (\( \Delta S \)) during the oxidation process. The relationship between \( \Delta G \), \( \Delta H \) (change in enthalpy), and \( \Delta S \) is given by the equation: \(\Delta G = \Delta H - T\Delta S\).
   • An increase in temperature may lead to a change in the slope of the plot due to entropy considerations, but this does not imply that \( \Delta S \) itself continually increases as you move from left to right.
   • The characteristic slopes of the lines are specific to each reaction and do not universally imply an increase in \( \Delta S \) from left to right on the diagram. Hence, Statement II is false.

Based on the above analysis, the correct answer is: Statement I is true but Statement II is false.