In physisorption adsorbent does not show specificity for any particular gas because ……..

Options

A. Involved van der Waals' forces are universal
B. gases involved behave like ideal gases
C. enthalpy of adsorption is low
D. it is a reversible process

Explanation

**Step-by-Step Solution:**

1. **Understanding Physisorption**: Physisorption is a type of adsorption where the adsorbate (gas) adheres to the surface of the adsorbent (solid) through weak intermolecular forces, primarily Van der Waals forces.

2. **Identifying the Nature of Van der Waals Forces**: Van der Waals forces are universal attractive forces that exist between all molecules, regardless of their specific chemical nature. This means that these forces are not unique to any particular gas.

3. **Analyzing the Options**:
- **Option 1**: "Involved Van der Waals forces are universal." This option suggests that since Van der Waals forces are present between all molecules, the adsorbent does not show specificity for any particular gas. This is a valid reason.
- **Option 2**: "Gases involved behave like ideal gases." This is not relevant to the specificity of adsorption.
- **Option 3**: "Enthalpy of adsorption is low." While it is true that the enthalpy of physisorption is low, it does not explain the lack of specificity.
- **Option 4**: "It is a reversible process." Although physisorption is reversible, this characteristic does not relate to the specificity of the adsorbent.

4. **Conclusion**: The correct answer is **Option 1**: "Involved Van der Waals forces are universal." This explains why physisorption does not show specificity for any particular gas.