Why are powdered substance more effective as adsorbents than their crystalline forms ?

Options

A. adsorption is an exothermic process
B. they become insert and do not react with the adsorbate
C. the extent of adsorption increases with increases in surface area of the adsorbent
D. adsorption is more if the size of adsorbent is small.

Explanation

To answer the question "Why are powdered substances more effective as adsorbents than their crystalline forms?", we can break down the explanation into several key points:

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is the process by which atoms, ions, or molecules from a gas, liquid, or dissolved solid adhere to a surface. This process is crucial in various applications, including catalysis, separation processes, and environmental remediation.

2. **Crystalline vs. Powdered Form**:
- Crystalline substances have a well-defined, ordered structure with a specific arrangement of atoms or molecules. This structure limits the surface area available for adsorption.
- When a crystalline substance is powdered, it breaks down into smaller particles, significantly increasing the total surface area available for adsorption.

3. **Surface Area and Adsorption**:
- The effectiveness of an adsorbent is largely dependent on its surface area. A larger surface area allows more molecules of the adsorbate (the substance being adsorbed) to interact with the adsorbent.
- The rate of physisorption (a type of adsorption that occurs due to weak van der Waals forces) is directly proportional to the surface area of the adsorbent. Therefore, more surface area leads to a higher rate of adsorption.

4. **Conclusion**:
- In summary, powdered substances are more effective as adsorbents than their crystalline forms because the process of powdering increases the surface area available for adsorption, which in turn enhances the rate of adsorption.

### Final Answer:
Powdered substances are more effective as adsorbents than their crystalline forms because the powdered form has a greater surface area, which increases the rate of adsorption.