In a chemical reaction , a catalyst used for

Options

A. Decreases the energy of activation
B. Increases the energy of activation
C. Does not change energy of activation
D. Decreases or increases the energy of activation

Answer

To solve the question regarding the role of a catalyst in a chemical reaction, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Role of a Catalyst**:
- A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It achieves this by providing an alternative reaction pathway.

**Hint**: Remember that catalysts are not consumed in the reaction and can be used repeatedly.

2. **Activation Energy Concept**:
- Activation energy (Ea) is the minimum energy required for a chemical reaction to occur. It is the energy barrier that reactants must overcome to form products.

**Hint**: Think of activation energy as a hill that reactants need to climb over to transform into products.

3. **Effect of a Catalyst on Activation Energy**:
- A catalyst lowers the activation energy required for the reaction. By doing so, it makes it easier for the reactants to convert into products, thus increasing the reaction rate.

**Hint**: A catalyst provides a shortcut, lowering the hill (activation energy) that reactants need to climb.

4. **Evaluating the Options**:
- The options given are:
- A) Decrease the energy of activation
- B) Increase the energy of activation
- C) Does not change the energy of activation
- D) Decreases or increases the energy of activation
- Based on our understanding, the correct answer is that a catalyst decreases the energy of activation.

**Hint**: Focus on the fundamental property of catalysts—they lower the activation energy.

5. **Conclusion**:
- Therefore, the correct answer to the question is **A) decreases the energy of activation**.

### Final Answer:
**A) Decreases the energy of activation**