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 which factor does not increase the rate of a chemical reaction, we will analyze each of the provided options step by step.

### Step 1: Analyze Increasing Temperature
- Increasing the temperature generally increases the kinetic energy of the molecules involved in the reaction.
- As the temperature rises, the frequency and energy of collisions between reactant molecules increase, leading to a higher rate of reaction.

**Conclusion**: Increasing temperature increases the rate of reaction.

### Step 2: Analyze Suitable Positive Catalyst
- A catalyst is a substance that increases the rate of a reaction without being consumed in the process.
- A suitable positive catalyst lowers the activation energy required for the reaction to occur, facilitating more effective collisions between reactant molecules.

**Conclusion**: Using a suitable positive catalyst increases the rate of reaction.

### Step 3: Analyze Increasing Concentration of Reactants
- According to the law of mass action, the rate of a reaction is directly proportional to the concentration of the reactants.
- Increasing the concentration of reactants leads to more frequent collisions, which in turn increases the rate of reaction.

**Conclusion**: Increasing the concentration of reactants increases the rate of reaction.

### Step 4: Analyze Increasing Activation Energy
- Activation energy is the minimum energy required for reactants to undergo a chemical reaction.
- If the activation energy is increased, fewer molecules will have enough energy to overcome this threshold, resulting in fewer effective collisions.

**Conclusion**: Increasing activation energy decreases the rate of reaction.

### Final Answer
From the analysis, we find that the only factor that does not increase the rate of reaction is **increasing activation energy**. Therefore, the correct answer is option **D**.

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