Catalyst increases the rate by

Options

A. Decreasesing `E_(a)`
B. Increasing `E_(a)`
C. Decreasing entropy
D. Increasing entropy

Explanation

To solve the question regarding how a catalyst increases the rate of a reaction, we can follow these 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 pathway for the reaction with a lower activation energy.

2. **Defining Activation Energy**:
Activation energy (Ea) is the minimum energy required for reactants to undergo a chemical reaction. It represents the energy barrier that must be overcome for the reactants to be converted into products.

3. **Analyzing the Rate of Reaction**:
The rate of a reaction can be described by the rate constant (k) in the Arrhenius equation:
\[ k = A e^{-\frac{E_a}{RT}} \]
where:
- \( k \) = rate constant
- \( A \) = pre-exponential factor (frequency factor)
- \( E_a \) = activation energy
- \( R \) = universal gas constant
- \( T \) = temperature in Kelvin

4. **Effect of Decreasing Activation Energy**:
From the Arrhenius equation, we can see that if the activation energy (Ea) is decreased, the exponent becomes less negative, which increases the value of \( k \). Since the rate of reaction is directly proportional to the rate constant, an increase in \( k \) leads to an increase in the rate of reaction.

5. **Conclusion**:
Therefore, a catalyst increases the rate of a reaction by decreasing the activation energy required for the reaction to occur. This allows more reactant molecules to have sufficient energy to undergo effective collisions, thus speeding up the reaction.

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

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