Which adsorption has low enthalpy of adsorption ?

Answer

To determine which type of adsorption has a low enthalpy of adsorption, we need to explore the concepts of physisorption and chemisorption.

### Step-by-Step Solution:

1. **Define Adsorption**:
- Adsorption is the process where atoms, ions, or molecules from a gas, liquid, or dissolved solid adhere to a surface.

2. **Types of Adsorption**:
- There are two main types of adsorption:
- **Physisorption**: This is a physical adsorption process where the adsorbate is held to the adsorbent by weak Van der Waals forces.
- **Chemisorption**: This is a chemical adsorption process where the adsorbate forms strong chemical bonds with the adsorbent.

3. **Enthalpy of Adsorption**:
- The enthalpy of adsorption is the heat change that occurs when a substance is adsorbed onto a surface. It is an important factor in determining the nature of the adsorption process.

4. **Enthalpy Values**:
- For **physisorption**, the enthalpy of adsorption is relatively low, typically in the range of 20 to 40 kJ/mol. This is due to the weak interactions (Van der Waals forces) involved.
- For **chemisorption**, the enthalpy of adsorption is much higher, ranging from 80 to 240 kJ/mol, because it involves the formation of stronger chemical bonds.

5. **Conclusion**:
- Since physisorption involves weak interactions and results in lower energy changes, it has a low enthalpy of adsorption compared to chemisorption. Therefore, the type of adsorption that has low enthalpy of adsorption is **physisorption**.

### Final Answer:
**Physisorption has low enthalpy of adsorption.**