Which of the following is correct about the equlibrium ?

Options

A. Cayalyst has no effect on equlibrium state
B. `K_(aq)` changes with temperatue
C. Value of `K_(eq)` changes by increasing concentration of equilibrium
D. `Delta G=0`

Answer

To determine which statements about equilibrium are correct, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Equilibrium**:
- Equilibrium in a chemical reaction is reached when the rate of the forward reaction equals the rate of the backward reaction. At this point, the concentrations of reactants and products remain constant over time.

2. **Analyzing the First Statement**:
- **Statement**: A catalyst has no effect on equilibrium state.
- **Explanation**: This statement is **correct**. A catalyst speeds up both the forward and reverse reactions equally, thus helping the system reach equilibrium faster, but it does not change the position of equilibrium or the equilibrium constant (K_eq).

3. **Analyzing the Second Statement**:
- **Statement**: The constant of equilibrium (K_eq) changes with temperature.
- **Explanation**: This statement is also **correct**. The equilibrium constant is temperature-dependent. For exothermic reactions, increasing the temperature decreases K_eq, while for endothermic reactions, increasing the temperature increases K_eq.

4. **Analyzing the Third Statement**:
- **Statement**: The value of K_eq changes by increasing the concentration of equilibrium.
- **Explanation**: This statement is **incorrect**. Changing the concentration of reactants or products does not change the value of K_eq. Instead, it shifts the position of equilibrium according to Le Chatelier's principle, but K_eq remains constant at a given temperature.

5. **Analyzing the Fourth Statement**:
- **Statement**: ΔG° (Gibbs free energy change) is equal to zero at equilibrium.
- **Explanation**: This statement is **correct**. At equilibrium, there is no net change in the concentrations of reactants and products, which means the Gibbs free energy change (ΔG°) is zero.

### Conclusion:
Based on the analysis:
- The correct statements are:
- **First Statement**: A catalyst has no effect on equilibrium state. (Correct)
- **Second Statement**: The constant of equilibrium (K_eq) changes with temperature. (Correct)
- **Fourth Statement**: ΔG° is equal to zero at equilibrium. (Correct)
- The incorrect statement is:
- **Third Statement**: The value of K_eq changes by increasing concentration of equilibrium. (Incorrect)

Thus, the correct options are the first, second, and fourth statements.