which one of the following statements is not correct ?

Options

A. Catalyst does not initiate any reaction
B. the value of equilibrium constant is changed in the presence of a catalyst in the reaction equilibrium
C. Enzymes catalyse mainly biochemical reaction
D. Coenzymes increase the catalytic activity of enzyme

Explanation

To determine which statement is not correct regarding catalysts, we will analyze each statement one by one.

### Step 1: Analyze the first statement
**Statement:** "Catalyst does not initiate any reaction."
- **Explanation:** This statement is correct. A catalyst does not initiate a reaction; it only provides an alternative pathway with a lower activation energy for the reaction to occur. It speeds up the reaction without being consumed in the process.

### Step 2: Analyze the second statement
**Statement:** "The value of equilibrium constant is changed in presence of catalyst in the reaction equilibrium."
- **Explanation:** This statement is incorrect. The presence of a catalyst does not change the equilibrium constant (K). A catalyst speeds up both the forward and reverse reactions equally, thus it does not affect the position of equilibrium or the value of K.

### Step 3: Analyze the third statement
**Statement:** "Enzymes are catalysts mainly in biological reactions."
- **Explanation:** This statement is correct. Enzymes are indeed biological catalysts that facilitate biochemical reactions in living organisms.

### Step 4: Analyze the fourth statement
**Statement:** "Coenzymes increase the catalytic activity of enzymes."
- **Explanation:** This statement is also correct. Coenzymes are organic molecules that assist enzymes in catalyzing reactions, thereby increasing their activity.

### Conclusion
After analyzing all the statements, the one that is not correct is the second statement: "The value of equilibrium constant is changed in presence of catalyst in the reaction equilibrium."

### Final Answer
The incorrect statement is: **B. The value of equilibrium constant is changed in presence of catalyst in the reaction equilibrium.**

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