Which of the following is not correct ?

Options

A. `Delta G` is zero for a reversible reaction
B. `Delta G` is positive for a spontaneous reaction
C. `Delta G` is negative for a spontaneous reaction
D. `Delta G` is positive for a non-spontaneous reaction.

Explanation

To determine which statement about Gibbs free energy (ΔG) is not correct, we need to analyze each option based on the principles of thermodynamics.

### Step-by-Step Solution:

1. **Understanding Gibbs Free Energy (ΔG)**:
- ΔG is a thermodynamic potential that indicates the spontaneity of a reaction.
- If ΔG < 0, the reaction is spontaneous.
- If ΔG > 0, the reaction is non-spontaneous.
- If ΔG = 0, the reaction is at equilibrium (reversible).

2. **Analyzing the Options**:
- **Option A**: "ΔG is 0 for a reversible reaction."
- This statement is correct because at equilibrium, the Gibbs free energy change is zero.

- **Option B**: "ΔG is positive for a spontaneous reaction."
- This statement is incorrect. For a spontaneous reaction, ΔG must be negative, not positive.

- **Option C**: "ΔG is negative for a spontaneous reaction."
- This statement is correct as it aligns with the definition of spontaneity in thermodynamics.

- **Option D**: "ΔG is positive for a non-spontaneous reaction."
- This statement is also correct because a non-spontaneous reaction has a positive ΔG.

3. **Conclusion**:
- The only incorrect statement among the options is **Option B**: "ΔG is positive for a spontaneous reaction."

### Final Answer:
**Option B is not correct.**

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