Chemisorption forms ………………. Molecular layers .

Answer

To solve the question "Chemisorption forms ………………. Molecular layers," we need to understand the concept of chemisorption and how it differs from physisorption.

### Step-by-Step Solution:

1. **Understanding Chemisorption**:
- Chemisorption is a type of adsorption where a chemical bond is formed between the adsorbate (the substance being adsorbed) and the adsorbent (the surface on which adsorption occurs). This process is typically stronger than physisorption, which involves weaker van der Waals forces.

2. **Characteristics of Chemisorption**:
- In chemisorption, the adsorbate forms a strong bond with the adsorbent, which means that once the adsorbate is attached, it does not easily detach. This bond formation is often irreversible or only reversible under specific conditions.

3. **Layer Formation**:
- Since chemisorption involves the formation of strong chemical bonds, once an adsorbate molecule attaches to the adsorbent, it occupies a specific site on the surface. This means that each site can only be occupied by one adsorbate molecule.

4. **Conclusion on Molecular Layers**:
- Because each adsorbate molecule can only bond to one site on the adsorbent, chemisorption results in the formation of a single layer of adsorbate molecules. Therefore, it is referred to as forming "unimolecular layers" or "single molecular layers."

5. **Final Answer**:
- Thus, the correct completion of the statement is: "Chemisorption forms unimolecular layers."