In the presence of a catalyst, the heat evolved or absorbed during the reaction:

Options

A. increases
B. decreases
C. remains unchanged
D. may increase or decrease

Explanation

To solve the question regarding the effect of a catalyst on the heat evolved or absorbed during a reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understand 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 does this by providing an alternative pathway for the reaction with a lower activation energy.

2. **Activation Energy**: The activation energy (Ea) is the minimum energy required for a reaction to occur. A catalyst lowers this activation energy for both the forward and reverse reactions.

3. **Effect on Enthalpy**: The change in enthalpy (ΔH) of a reaction is a measure of the heat absorbed or released during the reaction. Importantly, the presence of a catalyst does not change the overall enthalpy change of the reaction. This is because it affects both the forward and reverse reactions equally.

4. **Conclusion**: Since the catalyst does not alter the enthalpy change (ΔH) of the reaction, the amount of heat evolved or absorbed during the reaction remains unchanged.

5. **Final Answer**: In the presence of a catalyst, the heat evolved or absorbed during the reaction remains unchanged.