Usually the rate of reaction increases by all the factors except one of the following.

Options

A. Increasing temperature
B. With suitable positive catalyst
C. Increasing concentration of the reactants
D. Increasing activation energy

Answer

To solve the question regarding the factors that usually increase the rate of a chemical reaction, we need to analyze each option provided and determine which one does not contribute to an increase in reaction rate.

### Step-by-Step Solution:

1. **Understand the Factors Affecting Reaction Rate**:
- The rate of a chemical reaction can be influenced by several factors including temperature, concentration of reactants, presence of a catalyst, and activation energy.

2. **Evaluate Each Option**:
- **Option 1: Increasing Temperature**:
- According to the Arrhenius equation, increasing the temperature generally increases the rate of reaction because it provides more energy to the reactant molecules, allowing them to overcome the activation energy barrier more easily.
- **Conclusion**: This factor increases the rate of reaction.

- **Option 2: Presence of a Catalyst**:
- Catalysts lower the activation energy required for a reaction to occur, thus increasing the rate of reaction.
- **Conclusion**: This factor increases the rate of reaction.

- **Option 3: Concentration of Reactants**:
- Increasing the concentration of reactants typically leads to more frequent collisions between molecules, which increases the rate of reaction.
- **Conclusion**: This factor increases the rate of reaction.

- **Option 4: Increasing Activation Energy**:
- Increasing the activation energy makes it harder for reactants to convert into products because more energy is required to overcome the barrier. This results in a decrease in the rate of reaction.
- **Conclusion**: This factor does not increase the rate of reaction; it decreases it.

3. **Identify the Correct Answer**:
- Based on the analysis, the factor that does not increase the rate of reaction is **Option 4: Increasing Activation Energy**.

### Final Answer:
The factor that does not increase the rate of reaction is **Increasing Activation Energy**.

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