JEE Important Topic - Physisorption

Physisorption is an important topic in JEE Chemistry, particularly in the Surface Chemistry chapter. It refers to the physical adsorption of molecules onto a surface, driven primarily by van der Waals forces (weak intermolecular forces) rather than chemical bonds.

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Key Concepts:

1. Nature of Forces: In physisorption, the molecules are held to the surface by weak van der Waals forces, making it reversible.
2. Temperature Dependency: It is favored at low temperatures because weak forces are more effective at low kinetic energy.
3. Pressure Dependency: Physisorption increases with increasing pressure because more molecules can interact with the surface.
4. Extent of Adsorption: Adsorption increases with surface area, which is why finely divided solids like activated charcoal have high adsorption capacity.
5. No Chemical Reaction: No chemical bond forms, and the process is usually reversible.

Important Points for JEE:

• Understand the difference between physisorption and chemisorption (chemical adsorption).
• Study the Langmuir adsorption isotherm and how it explains physisorption behavior.
• Focus on factors affecting adsorption, such as temperature, pressure, and surface area.

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Applications:

• Catalysis: Physisorption plays a role in catalytic processes.
• Gas Storage: Materials like activated carbon adsorb gases through physisorption.

This topic is fundamental in understanding various phenomena in surface chemistry and has frequent questions in both theory and numerical formats in JEE exams.

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