Which one of the following is not a correct statement

Options

A. Physical adsorption is reversible in nature
B. Physical adsorption involves vander waals forces
C. Rate of physical adsorption increases with increase of pressure on the adsorbate
D. High active energy is involved

Answer

To determine which statement is not correct regarding physical adsorption, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Physical Adsorption**:
- Physical adsorption occurs when gas molecules adhere to a solid surface through weak intermolecular forces, specifically van der Waals forces. There is no formation of chemical bonds.

2. **Analyzing the Statements**:
- **Statement 1**: "Physical adsorption is reversible in nature."
- **Analysis**: This statement is correct. Physical adsorption can be reversed by changing conditions such as temperature or pressure, allowing the adsorbate to desorb.

- **Statement 2**: "Physical adsorption involves van der Waals forces."
- **Analysis**: This statement is also correct. The forces involved in physical adsorption are indeed weak van der Waals forces.

- **Statement 3**: "Rate of physical adsorption increases with increase of pressure on the adsorbate."
- **Analysis**: This statement is correct as well. Increasing the pressure of the adsorbate typically increases the rate of adsorption due to a higher concentration of adsorbate molecules available to adhere to the surface.

- **Statement 4**: "High activation energy is involved for physical adsorption."
- **Analysis**: This statement is incorrect. Physical adsorption involves low activation energy, typically in the range of 5 to 40 kJ/mol, which is much lower than the activation energy for chemical adsorption (40 to 800 kJ/mol).

3. **Conclusion**:
- The statement that is not correct is **Statement 4**: "High activation energy is involved for physical adsorption."

### Final Answer:
The statement that is not correct is: **"High activation energy is involved for physical adsorption."**

---