Adsorption is the tendency of accumulation of molecular species at the surface of solid or liquid. Depending upon the nature of bonds or forces of attraction between adsorbate and adsorbent. It is classofied between physisorption and chemisorption.
Which of the following gas molecules have maximum value enthalpy of physisorption?

Options

A. `C_(2)H_(6)`
B. `Ne`
C. `H_(2)`
D. `H_(2)O`

Explanation

To determine which gas molecule has the maximum value of enthalpy of physisorption, we need to understand the concept of physisorption and the factors that influence the enthalpy of adsorption.

### Step-by-Step Solution:

1. **Understanding Physisorption**:
- Physisorption is a type of adsorption that occurs due to weak Van der Waals forces. It is a physical process where the adsorbate molecules accumulate on the surface of the adsorbent without forming strong chemical bonds.

2. **Identify the Molecules**:
- The given options are:
- (a) C2H6 (Ethane)
- (b) Ne (Neon)
- (c) H2 (Hydrogen)
- (d) H2O (Water)

3. **Analyzing the Molecules**:
- **Ethane (C2H6)**: A larger molecule with some Van der Waals interactions.
- **Neon (Ne)**: A noble gas with very weak Van der Waals forces due to its monoatomic nature.
- **Hydrogen (H2)**: A diatomic molecule with weak Van der Waals forces.
- **Water (H2O)**: A polar molecule that can form hydrogen bonds, which are stronger than typical Van der Waals forces.

4. **Comparing Enthalpy of Physisorption**:
- The enthalpy of physisorption is influenced by the strength of the interactions between the adsorbate and the adsorbent.
- Water can form hydrogen bonds in addition to Van der Waals forces, making its enthalpy of physisorption higher compared to the other molecules listed.

5. **Conclusion**:
- Among the given options, water (H2O) has the maximum value of enthalpy of physisorption due to its ability to form hydrogen bonds, which are relatively stronger than the Van der Waals forces present in the other molecules.

### Final Answer:
The gas molecule with the maximum value of enthalpy of physisorption is **H2O (Water)**.