In physical adsorption, gas molecules are bound on the solid surface by

Options

A. Chemical forces
B. Electrostatic forces
C. Gravitational forces
D. Van der Waal’s forces

Answer

To answer the question "In physical adsorption, gas molecules are bound on the solid surface by," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is a surface phenomenon where molecules (adsorbates) accumulate on the surface of a solid (adsorbent) rather than penetrating into the bulk of the solid.

2. **Types of Adsorption**:
- There are two main types of adsorption: physical (physisorption) and chemical (chemisorption).
- Physical adsorption involves weak interactions, while chemical adsorption involves stronger interactions.

3. **Forces in Physical Adsorption**:
- In physical adsorption, the gas molecules are held on the solid surface primarily by weak forces.
- These forces are known as **van der Waals forces**. They are much weaker than chemical bonds and include attractions such as dipole-dipole interactions, dipole-induced dipole interactions, and London dispersion forces.

4. **Conclusion**:
- Therefore, in physical adsorption, gas molecules are bound on the solid surface by **weak van der Waals forces**.

### Final Answer:
In physical adsorption, gas molecules are bound on the solid surface by **weak van der Waals forces**.

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