Physical adsorption of a gaseous species may change to chemical adsorption with ……..

Options

A. decrease in temperature
B. increase in temperature
C. increase in surface area of adsorbent
D. decrease in surface area of adsorbent

Explanation

To solve the question regarding the transition from physical adsorption to chemical adsorption, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Physical Adsorption**:
- Physical adsorption occurs when a gas (adsorbate) adheres to a solid surface (adsorbent) through weak Van der Waals forces. This type of adsorption is generally reversible and does not involve significant energy changes.

2. **Factors Affecting Adsorption**:
- The nature of the interaction between the adsorbate and adsorbent is crucial. In physical adsorption, the forces are weak, and the process is influenced by temperature and pressure.

3. **Effect of Temperature on Physical Adsorption**:
- When the temperature increases, the kinetic energy of the gas molecules also increases. This can lead to the overcoming of the weak Van der Waals forces, resulting in desorption. Therefore, high temperatures are not favorable for physical adsorption.

4. **Transition to Chemical Adsorption**:
- Chemical adsorption (chemisorption) involves the formation of stronger chemical bonds between the adsorbate and adsorbent. This process requires a certain amount of energy, known as activation energy, to overcome the energy barrier for bond formation.

5. **Role of Increased Temperature**:
- When the temperature is increased, the energy supplied can reach the activation energy required for the formation of chemical bonds. This allows the gaseous adsorbate to interact more strongly with the solid adsorbent, leading to chemical adsorption.

6. **Conclusion**:
- Therefore, the transition from physical adsorption to chemical adsorption occurs with an increase in temperature. This is because the increased thermal energy facilitates the formation of stronger chemical bonds.

### Final Answer:
The physical adsorption of a gaseous species may change to chemical adsorption with **increase in temperature**.