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 solve the question, we need to analyze the statements regarding Gibbs free energy (ΔG) and determine which one is not correct.

### Step-by-Step Solution:

1. **Understanding Gibbs Free Energy (ΔG)**:
- Gibbs free energy is a thermodynamic potential that helps predict the direction of chemical reactions and phase changes.
- The sign of ΔG indicates whether a reaction is spontaneous or non-spontaneous.

2. **Analyzing the Statements**:
- **Statement 1**: "ΔG is 0 for a reversible reaction."
- This is correct. At equilibrium, the Gibbs free energy change (ΔG) is 0, indicating that the forward and reverse reactions occur at the same rate.

- **Statement 2**: "ΔG is positive for a spontaneous reaction."
- This is incorrect. A spontaneous reaction has a negative ΔG, meaning it can occur without external input.

- **Statement 3**: "ΔG is negative for a spontaneous reaction."
- This is correct. A negative ΔG indicates that the reaction is spontaneous.

- **Statement 4**: "ΔG is positive for a non-spontaneous reaction."
- This is correct. A positive ΔG indicates that the reaction is non-spontaneous and requires energy input to occur.

3. **Conclusion**:
- The only incorrect statement is Statement 2, which claims that ΔG is positive for a spontaneous reaction.

### Final Answer:
The statement that is not correct is: "ΔG is positive for a spontaneous reaction."

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