A catalyst

Options

A. Increases the heat of the reaction
B. Decreases the heat of the reaction
C. Does not alter the heat of the reaction
D. Increases the number of collisions

Answer

### 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 with a lower activation energy.

2. **Activation Energy**: Activation energy is the minimum energy required for a reaction to occur. In the presence of a catalyst, the activation energy needed for the reactants to reach the transition state is reduced.

3. **Graphical Representation**: In a typical energy diagram:
- The x-axis represents the progress of the reaction.
- The y-axis represents the energy of the system.
- The reactants start at a certain energy level, and as the reaction progresses, they reach a peak (the transition state) before forming products at a lower energy level (in an exothermic reaction).

4. **Effect of Catalyst on Activation Energy**: When a catalyst is introduced:
- The activation energy for the forward reaction decreases (shown by a lower peak in the energy diagram).
- The activation energy for the reverse reaction also decreases, but the overall change in enthalpy (ΔH) remains unchanged.

5. **Conclusion**: The presence of a catalyst does not alter the heat of the reaction (ΔH). It only affects the rate by lowering the activation energy required for the reaction to proceed.

### Final Answer:
A catalyst does not alter the heat of the reaction.

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