The incorrect statement among the following

Options

A. a. A catalyst does not initiate the reaction
B. b. The action of catalyst in many instances is selective
C. c. Catalyst may loose its catalytic activity at high temperature
D. d. The composition of catalyst changes at the end of reaction

Answer

To determine the incorrect statement among the given options regarding catalysts, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** "Catalyst does not initiate the reaction."
- A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent change itself. While it may not initiate a reaction in all cases, it can be necessary for some reactions to occur. Therefore, this statement is incorrect.

### Step 2: Analyze Statement B
**Statement B:** "The action of catalyst may, in many instances, be selective."
- Catalysts can indeed be selective, meaning they can favor certain reactions over others. This is a true statement.

### Step 3: Analyze Statement C
**Statement C:** "Catalyst may lose its catalytic activity at high temperature."
- Catalysts have an optimum temperature range within which they function effectively. If the temperature exceeds this range, the catalyst may lose its activity. Thus, this statement is also true.

### Step 4: Analyze Statement D
**Statement D:** "The composition of catalyst changes at the end of reaction."
- By definition, a catalyst is not consumed in the reaction and should remain unchanged in composition at the end of the reaction. Therefore, this statement is incorrect.

### Conclusion
After analyzing all statements, we find that:
- **Incorrect Statement:** Statement A and Statement D are incorrect. However, since the question asks for the incorrect statement among the options, we conclude that **Statement D is the most explicitly incorrect regarding the definition of a catalyst.**

### Final Answer
The incorrect statement is **D: The composition of catalyst changes at the end of reaction.**

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