There is an exception but I do not remember that example right now. Please answer if anyone knows that example.

Endothermic Adsorption

Endothermic adsorption refers to a process in which the adsorption of a substance onto the surface of another substance requires the absorption of heat or energy from the surroundings. This type of adsorption is characterized by a decrease in temperature during the adsorption process. It is important to note that adsorption itself is a process that involves the accumulation of molecules or particles on the surface of a solid or liquid substance.

Example of Endothermic Adsorption

One example of endothermic adsorption is the adsorption of ammonia (NH3) onto activated carbon. This process is commonly used in air conditioning and refrigeration systems.

The Process
1. Surface Activation: Activated carbon is a highly porous material with a large surface area, which is essential for effective adsorption. The carbon is treated with steam or chemicals to increase its porosity and create more adsorption sites.

2. Gas-Phase Adsorption: Ammonia gas is introduced into the system containing the activated carbon. The gas molecules come into contact with the carbon surface and start to adsorb.

3. Heat Absorption: As the ammonia molecules adsorb onto the carbon surface, energy is required to break the attractive forces between the ammonia molecules and the surrounding gas phase. This energy is obtained from the surroundings, resulting in a decrease in temperature.

4. Adsorbed Layer Formation: The ammonia molecules continue to adsorb onto the activated carbon surface until equilibrium is reached. At this point, the adsorbed layer is formed, consisting of a monolayer or multilayer of ammonia molecules attached to the carbon surface.

5. Refrigeration Effect: The decrease in temperature during the adsorption process can be harnessed for refrigeration purposes. In air conditioning and refrigeration systems, the adsorption of ammonia onto activated carbon is used to cool the air or refrigerant, providing a cooling effect.

Key Points:
- Endothermic adsorption involves the absorption of heat or energy from the surroundings.
- The adsorption of ammonia onto activated carbon is an example of endothermic adsorption.
- Surface activation of activated carbon increases its porosity and adsorption capacity.
- Ammonia gas is adsorbed onto the carbon surface, requiring energy and resulting in a decrease in temperature.
- The refrigeration effect of endothermic adsorption is utilized in air conditioning and refrigeration systems.