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

To analyze the Gibbs free energy (G) vs extent of reaction graph, consider the following:
A spontaneous reaction occurs where G decreases, until the reaction reaches equilibrium. At equilibrium, G is minimized, and any deviation will increase it.
Let's evaluate each statement:

1. Statement A: "Reaction is spontaneous at (a) and (b)."
   - At point (a), G is decreasing, so the reaction is spontaneous.
   - Near equilibrium at point (b), the change in G is zero. This makes the reaction neither spontaneous nor non-spontaneous.
   - This statement is false.
2. Statement B: "Reaction is at equilibrium at point (b) and nonspontaneous at point (c)."
   - At point (b), G is at a minimum, indicating equilibrium.
   - At point (c), G is increasing, indicating a nonspontaneous reaction.
   - This statement is true.
3. Statement C: "Reaction is spontaneous at (a) and nonspontaneous at (c)."
   - Correct as explained in A and B: G is decreasing at (a) and increasing at (c).
   - This statement is true.
4. Statement D: "Reaction is non-spontaneous at (a) and (b)."
   - Incorrect as discussed: (a) is spontaneous, and (b) is equilibrium.
   - This statement is false.

The number of true statements is 2, which fits the given range (2,2).