The correct explanation for the effect of catalyst on the rate of reversible reaction is

Options

A. It displaces the equilibrium state on right side
B. It increases the kinetic energy of reacting molecules
C. It provides a new reaction path of low activation energy
D. It decreases the the velocity of backward reaction

Answer

To solve the question regarding the effect of a catalyst on the rate of a reversible reaction, we will analyze the concept step by step.

### Step-by-Step Solution:

1. **Understanding Reversible Reactions**:
- A reversible reaction is one where the products can react to form the original reactants. This process can occur in both directions, and the system remains in a state of equilibrium with its surroundings.

**Hint**: Remember that in reversible reactions, both forward and backward reactions occur simultaneously.

2. **Role of Catalysts**:
- A catalyst is a substance that increases the rate of a reaction without being consumed in the process. It achieves this by providing an alternative pathway for the reaction with a lower activation energy.

**Hint**: Think of a catalyst as a facilitator that helps the reaction proceed more easily.

3. **Activation Energy**:
- Activation energy (Ea) is the minimum energy required for reactants to convert into products. In the absence of a catalyst, the reaction has a certain activation energy barrier.

**Hint**: Activation energy is crucial because it determines how quickly a reaction can occur.

4. **Effect of Catalyst on Activation Energy**:
- When a catalyst is introduced, it lowers the activation energy required for both the forward and backward reactions. This means that more reactant molecules have enough energy to overcome the energy barrier, thus increasing the rate of reaction.

**Hint**: Lower activation energy means that more molecules can participate in the reaction at a given temperature.

5. **Equilibrium Consideration**:
- While a catalyst speeds up the attainment of equilibrium, it does not change the position of the equilibrium itself. The ratio of products to reactants at equilibrium remains the same.

**Hint**: A catalyst does not favor either the forward or backward reaction; it simply helps both occur faster.

6. **Evaluating Options**:
- Based on the above understanding, we can evaluate the given options:
- **Option 1**: Incorrect, as a catalyst does not displace the equilibrium state.
- **Option 2**: Incorrect, as a catalyst does not increase the kinetic energy of molecules.
- **Option 3**: Correct, as it provides a new reaction path of lower activation energy.
- **Option 4**: Incorrect, as a catalyst does not decrease the velocity of the backward reaction.

**Hint**: Always check if the statement aligns with the fundamental principles of catalysis and equilibrium.

### Conclusion:
The correct explanation for the effect of a catalyst on the rate of a reversible reaction is that it provides a new reaction path of lower activation energy, allowing the reaction to reach equilibrium more quickly without altering the equilibrium position.

**Final Answer**: Option 3 - It provides a new reaction path of low activation energy.