If a chemical reaction is at equilibrium, which of the following is not correct?

Options

A. `triangleG^(0)=0`
B. `K_(p)=1`
C. `K_(c)=1`
D. `triangleG^(0)=1`

Answer

To determine which statement about a chemical reaction at equilibrium is not correct, we need to analyze the properties of equilibrium and the Gibbs free energy (ΔG) associated with it.

### Step-by-Step Solution:

1. **Understanding Equilibrium**: At equilibrium, the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant over time.

2. **Gibbs Free Energy (ΔG)**: The Gibbs free energy change (ΔG) is a crucial indicator of the spontaneity of a reaction.
- If ΔG < 0, the reaction is spontaneous in the forward direction.
- If ΔG > 0, the reaction is non-spontaneous in the forward direction.
- If ΔG = 0, the system is at equilibrium.

3. **Relationship Between ΔG and Equilibrium Constant (K)**: The relationship between ΔG and the equilibrium constant (K) can be expressed as:
\[ ΔG = ΔG^\circ + RT \ln K \]
At equilibrium, ΔG = 0, which leads to:
\[ 0 = ΔG^\circ + RT \ln K \]
Rearranging gives:
\[ ΔG^\circ = -RT \ln K \]
This indicates that when K = 1 (which corresponds to ln K = 0), ΔG = 0, confirming that the system is at equilibrium.

4. **Evaluating the Options**: We need to evaluate the given options to identify which statement is incorrect.
- If the options state that ΔG = 0 at equilibrium, that is correct.
- If they state that K = 1 at equilibrium, that is also correct.
- If they mention any other condition that contradicts the above, that would be the incorrect statement.

5. **Conclusion**: Based on the analysis, if the first three options are correct, the fourth option must be the incorrect one.

### Final Answer:
The statement that is not correct regarding a chemical reaction at equilibrium is the fourth option.