Which one of the following statements is not correct ?

Options

A. Catalyst does not initiate any reaction
B. The value of the equlibrium constant is changed in the presence of a catalyst in the reaction at equlibrium
C. Enzymes catalyse many bio-chemical reactions
D. Coenzymes increase catalytic activity of enzyme

Explanation

To determine which statement is not correct regarding catalysts and their effects on chemical reactions, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding the Role of Catalysts**:
- A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by lowering the activation energy required for the reaction to occur.

2. **Analyzing the Options**:
- **Option 1**: "Catalyst does not initiate any reaction."
- This statement is **correct**. Catalysts do not initiate reactions; they only speed up reactions that would occur naturally.

- **Option 2**: "The value of equilibrium constant is changed in the presence of catalyst in the reaction at equilibrium."
- This statement is **incorrect**. A catalyst does not change the equilibrium constant of a reaction. It only helps the system reach equilibrium faster without altering the position of equilibrium.

- **Option 3**: "Enzymes catalyze mainly many biochemical reactions."
- This statement is **correct**. Enzymes are biological catalysts that facilitate biochemical reactions in living organisms.

- **Option 4**: "Coenzymes increase the catalytic activity of enzymes."
- This statement is **correct**. Coenzymes are non-protein molecules that assist enzymes in catalyzing reactions, thus enhancing their activity.

3. **Conclusion**:
- The statement that is not correct is **Option 2**: "The value of equilibrium constant is changed in the presence of catalyst in the reaction at equilibrium."

### Final Answer:
The incorrect statement is **Option 2**.