What is physical adsorption.

Options

A. chemical adsoption
B. physical adsorption
C. both (a) and (b)
D. none of these

Answer

### Step-by-Step Solution:

1. **Definition of Physical Adsorption**:
Physical adsorption is a phenomenon where molecules of a substance are attracted and retained on the surface of a solid or liquid. This process occurs due to weak intermolecular forces known as Van der Waals forces.

2. **Nature of Forces Involved**:
The forces that facilitate physical adsorption are weak compared to chemical bonds. These Van der Waals forces arise from temporary dipoles that occur when molecules are in close proximity to each other.

3. **Example of Physical Adsorption**:
A common example of physical adsorption is the interaction between charcoal and ammonia (NH3). When ammonia gas comes into contact with charcoal, the ammonia molecules are attracted to the surface of the charcoal due to Van der Waals forces.

4. **Visualization of the Process**:
Imagine a piece of charcoal with ammonia molecules approaching it. The ammonia molecules will begin to adhere to the surface of the charcoal, demonstrating how physical adsorption occurs.

5. **Applications of Physical Adsorption**:
Physical adsorption is widely used in various applications, such as in charcoal masks, where charcoal adsorbs impurities and odors from the skin, thanks to its large surface area and the physical adsorption of substances.

6. **Conclusion**:
In summary, physical adsorption is a process characterized by the weak attraction of molecules to a surface, primarily facilitated by Van der Waals forces, and is exemplified by the adsorption of ammonia on charcoal.