A catalyst increases rate of reaction by:

Options

A. Decreasing enthalpy
B. Decreasing internal energy
C. Decreasing activation energy
D. Increasing activation energy

Explanation

To answer the question "A catalyst increases the rate of reaction by:", we will analyze the role of a catalyst in a chemical reaction step by step.

### 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.

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

3. **Effect of a Catalyst on Activation Energy**:
- A catalyst lowers the activation energy of a reaction. This means that the energy barrier that the reactants need to overcome is reduced.

4. **Increased Proportion of Reacting Particles**:
- By lowering the activation energy, a greater proportion of the reactant particles have enough energy to collide successfully and form products. This increases the likelihood of effective collisions.

5. **Conclusion**:
- Therefore, the correct statement is that a catalyst increases the rate of reaction by **decreasing activation energy**.

### Final Answer:
A catalyst increases the rate of reaction by **decreasing activation energy**.

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