Question

Consider the graph of Gibbs free energy G vs Extent of reaction. The number of statement/s from the following which are true with respect to points (a), (b) and (c) is…

A. Reaction is spontaneous at (a) and (b)  
B. Reaction is at equilibrium at point (b) and nonspontaneous at point (c)  
C. Reaction is spontaneous at (a) and nonspontaneous at (c)  
D. Reaction is non-spontaneous at (a) and (b)

Answer 1

Correct Answer: 2

Analysis of Gibbs Free Energy (G) vs Extent of Reaction

Key Concepts:

• The graph of \( G \) vs. extent of reaction (\( \xi \)) typically has a minimum point.
• The slope of the curve indicates spontaneity:
  • If \( \Delta G < 0 \), the reaction is spontaneous.
  • If \( \Delta G = 0 \), the reaction is at equilibrium.
  • If \( \Delta G > 0 \), the reaction is non-spontaneous.

Explanation of Points on the Graph:

1. Point (a):
   • At point (a), \( \Delta G < 0 \) (negative slope).
   • The reaction is spontaneous.
2. Point (b):
   • At point (b), \( \Delta G = 0 \) (slope = 0).
   • The reaction is at equilibrium.
3. Point (c):
   • At point (c), \( \Delta G > 0 \) (positive slope).
   • The reaction is non-spontaneous.

Given Statements:

• A: Reaction is spontaneous at (a) and (b) → False (it is not spontaneous at (b), as (b) is equilibrium).
• B: Reaction is at equilibrium at point (b) and non-spontaneous at point (c) → True.
• C: Reaction is spontaneous at (a) and non-spontaneous at (c) → True.
• D: Reaction is non-spontaneous at (a) and (b) → False.

Conclusion:

The number of true statements is 2 (Statements B and C).