Which is not correct for physical adsorption ?

Options

A. High pressure
B. Negative `Delta H`
C. Higher critical temperature of adsorbate
D. High temperature

Explanation

To determine which statement is not correct for physical adsorption, we will analyze each of the given options step by step.

### Step 1: Understanding Physical Adsorption
Physical adsorption, also known as physisorption, occurs due to weak Van der Waals forces between the adsorbent (the surface) and the adsorbate (the substance being adsorbed). It is characterized by the following features:

- It is generally reversible.
- It occurs at lower temperatures.
- It is favored by high pressures.

### Step 2: Analyzing Each Option
Now, let's evaluate each option provided in the question:

1. **High Pressure**:
- Physical adsorption is favored at high pressures because increasing pressure enhances the interaction between the adsorbent and adsorbate. More gas molecules can be pushed onto the surface of the solid adsorbent.
- **Conclusion**: This statement is correct for physical adsorption.

2. **Negative Enthalpy (ΔH)**:
- For adsorption processes, the enthalpy change (ΔH) is typically negative, indicating that energy is released when the adsorbate adheres to the adsorbent. This is true for both physical and chemical adsorption.
- **Conclusion**: This statement is correct for physical adsorption.

3. **High Critical Temperature of Adsorbate**:
- The critical temperature of an adsorbate is the temperature above which it cannot be liquefied, regardless of pressure. High critical temperatures indicate that the adsorbate is less volatile and can be effectively adsorbed.
- **Conclusion**: This statement is correct for physical adsorption.

4. **High Temperature**:
- High temperatures are generally unsuitable for physical adsorption. As temperature increases, the kinetic energy of the adsorbate molecules also increases, which can weaken the Van der Waals forces and lead to desorption of the adsorbate from the adsorbent.
- **Conclusion**: This statement is not correct for physical adsorption.

### Final Answer
The option that is **not correct for physical adsorption** is **Option 4: High Temperature**.