Substances which alter the velocity of a reaction by mere presence, without undergoing any change in mass and compossition are termed catalyst and the phenomenon is known as catalysis
According to the adsorption theroy of catalysis, the rate of reaction increases because

Options

A. According to the activation energy of the reaction.
B. Concentration of reactant molecules at the active centres of the catalyst becomes high due to adsorption.
C. Adsorption increases the activation energy of the reaction.
D. Adsorption decreases the activation of the energy of the reaction.

Answer

To solve the question regarding the increase in reaction rate due to catalysis according to the adsorption theory, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Definition of Catalyst and Catalysis**:
- A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent change in its mass or composition. The process of using a catalyst is called catalysis.

2. **Understanding Adsorption Theory**:
- According to the adsorption theory of catalysis, the catalyst works by providing a surface for the reactants to adhere to, which facilitates the reaction.

3. **Mechanism of Catalysis**:
- The catalysis process can be summarized in several steps:
- **Diffusion**: The reactants diffuse to the surface of the catalyst.
- **Adsorption**: The reactants are adsorbed onto the surface of the catalyst.
- **Formation of Intermediate**: The adsorbed reactants interact with the catalyst to form an intermediate complex.
- **Reaction**: This intermediate then reacts to form the final product.
- **Desorption**: Finally, the product is released (desorbed) from the surface of the catalyst.

4. **Effect on Activation Energy**:
- The presence of the catalyst lowers the activation energy required for the reaction to proceed. This means that the reaction can occur more readily than it would without the catalyst.

5. **Increase in Concentration of Reactants**:
- The adsorption of reactants on the catalyst surface increases their local concentration at the active sites of the catalyst. This higher concentration leads to an increased likelihood of collisions between reactant molecules, thereby increasing the reaction rate.

6. **Conclusion**:
- Therefore, according to the adsorption theory of catalysis, the rate of reaction increases because:
- The concentration of reactant molecules at the active centers of the catalyst becomes high due to adsorption.
- The adsorption process lowers the activation energy, which also contributes to an increased reaction rate.

### Final Answer:
The rate of reaction increases because the concentration of reactant molecules at the active centers of the catalyst becomes high due to adsorption, and the adsorption process decreases the activation energy.

---