Comprehension # 1
Many lyophilic sols and few lyophobic sols when coagulated under some special conditions changes into semi rigid mass, enclosing whole amount of liquid within itself, it is called gel and the process is called gelation, Gelatin Agar-agar, gum-Arabic can be converted into gels by cooling them under moderate concentration conditions. Hydrophobic sols like silicic acid. `Al(OH)_(3)` are prepared by double decomposition and exchange of solvent method.
Types of Gel :
(i) Elastic gel : Those gel which have elastic properties.
Ex : Gelatin, Strach, Agar-agar etc.
(ii) Non-elastic gel : Those gel which are rigid.
Ex : Silica gel.
Properties of Gel :
1. Syneresis/weeping of gel : The spontaneous liberation of liquid from a gel is called syneresis or weeping of gels. It is reverse of swelling.
Ex : Gelatin, Agar-Agar show syneresis at low concentration while sillicic acid shows it at high concentration.
2. Imbibition or swelling of gel : When gel is kept in a suitable liquid (water) it absorb large volume of liquid. The phenomenon is called imbibition or swelling of gel.
3. Thixotropic : Some gels when shaken to form a sol, on keeping changes into gel are termed as thixotropic gel and phenomenon is called thixotropy.
Ex : Gelatin and silica liquify on shaking changing into corresponding sol and sol on keeping changes back into gel.
Which of the following is used to adsorb water ?

Options

A. Silica gel
B. Calcium acetate
C. Hair gel
D. Cheese

Answer

To solve the question regarding which of the following is used to absorb water, we can follow these steps:

### Step 1: Understand the Concept of Gels
Gels are semi-rigid structures that can absorb liquids. They can be classified into two types: elastic gels and non-elastic gels. Elastic gels, like gelatin and agar-agar, have elastic properties, while non-elastic gels, like silica gel, are rigid.

### Step 2: Identify the Properties of Gels
From the comprehension provided, we know that gels exhibit specific properties:
- **Syneresis**: The process where a gel releases liquid.
- **Imbibition**: The process where a gel absorbs liquid, which is significant in our context.
- **Thixotropic**: Some gels can change from gel to sol upon shaking and revert back when left undisturbed.

### Step 3: Analyze the Options
We need to determine which gel is used to absorb water. Based on the properties mentioned:
- **Silica Gel**: It is a non-elastic gel known for its ability to absorb moisture from the environment. It is often used as a desiccant to keep things dry.
- **Other Gels**: While other gels like gelatin and agar-agar can swell and absorb water, they are not primarily known for this property in the context of desiccation.

### Step 4: Conclusion
Based on the properties of gels and their applications, the correct answer to the question is that silica gel is used to absorb water.

### Final Answer:
The correct option is **Silica Gel**.

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