How many layers are adsorbed in chemical adsorption?

Options

A. One
B. Two
C. Many
D. Zero

Answer

### Step-by-Step Text Solution:

1. **Understanding Adsorption**:
- Adsorption is the process where gas, liquid, or solid particles accumulate on a surface. The substance that accumulates is called the adsorbate, while the surface it accumulates on is called the adsorbent.

2. **Types of Adsorption**:
- There are two main types of adsorption: physical adsorption (physisorption) and chemical adsorption (chemisorption).
- In physisorption, the forces of attraction are weak (like van der Waals forces), and the process is generally reversible.
- In chemisorption, there is a strong chemical bond formed between the adsorbate and the adsorbent, making it irreversible.

3. **Characteristics of Chemical Adsorption**:
- Chemical adsorption occurs under specific conditions where a chemical reaction takes place between the adsorbate and the adsorbent.
- Once the chemical bond is formed, it is strong and difficult to break.

4. **Formation of Layers**:
- In the case of chemical adsorption, once the first layer of adsorbate is formed on the adsorbent, the surface is effectively covered.
- Since the requirement for chemical bonding is fulfilled only once, no further layers can be formed on top of the first layer.

5. **Conclusion**:
- Therefore, in chemical adsorption, only one layer (monolayer) of adsorbate is formed on the adsorbent.
- The answer to the question is that only **1 layer** is adsorbed in chemical adsorption.