Which one of the following is not the characteristic
of physiorption?

Options

A. Reversible in nature
B. Specific in nature
C. Low adsorption enthalpy
D. Depends on nature of gas

Answer

To determine which characteristic is not associated with physisorption, we need to analyze the properties of physisorption and evaluate the given options.

### Step-by-Step Solution:

1. **Understanding Physisorption**:
Physisorption, or physical adsorption, involves the adhesion of molecules to a surface through weak Van der Waals forces. It is characterized by its reversibility and relatively low energy changes.

2. **Evaluating the Options**:
- **Option A: Irreversible in nature**:
- This statement is incorrect for physisorption. Physisorption is reversible because it involves weak interactions. Therefore, this characteristic does not apply to physisorption.

- **Option B: Specific in nature**:
- This statement is also incorrect. Physisorption is not specific; it can occur with various molecules since it relies on weak forces rather than specific chemical interactions. Thus, this is a characteristic that does not apply to physisorption.

- **Option C: Low adsorption enthalpy**:
- This statement is correct. Physisorption typically has low adsorption enthalpy, usually in the range of 20 to 40 kJ/mol, which is characteristic of weak interactions.

- **Option D: Depends on the nature of gas**:
- This statement is also correct. The extent of physisorption can depend on the nature of the gas and the surface it is adsorbing onto.

3. **Conclusion**:
Based on the analysis, the characteristic that is **not** associated with physisorption is **Option B: Specific in nature**. Therefore, the correct answer is Option B.