Table of Contents
Physical adsorption is another name for physisorption, which is an exothermic process. It has a low adsorption enthalpy, at 20 to 40 kJ/mol. Normally, weak Van der Waals forces create the gas to collect just on solid objects during physisorption.
A Brief Outline
Because the adsorbent in the supplied surface does not indicate any particular gas, physisorption lacks specificity. It is reversible in nature, in that gas physisorption by a solid can be reverted to gas physisorption by a solid. Adsorption of gases such as hydrogen, nitrogen, and other gases on the surface of adsorbents such as charcoal is an example of physisorption.
Important concepts
Physisorption Characteristics
Specificity is lacking.
The force of van der Waals is global. As a result, an adsorbent’s surface does not display any preference for a particular gas.
The nature of adsorbate
The amount of gas absorbed by a material is determined by the gas’s composition.
Nature is reversible.
The physisorption of a gas by a material is usually reversible. As an outcome, it can be denoted as:
Solid + Gas ↔ Gas/Solid + Heat
The adsorbent’s surface area.
As the surface area of the adsorbent grows, the fraction of physisorption increases. As a result, finely split metals and porous materials with large surface areas are good adsorbents.
The enthalpy of physisorption
The process of physical adsorption is already exothermic. However, its enthalpy of adsorption is minimal, ranging between 20 and 40 kJ mol-1. The attraction between the gas molecules is the reason for this. The solid surface is generated due to weak van der Waals forces.
The building of van der Waals forces on the surface area lies at the heart of the physical adsorption process. The technique determines the porosity and surface areas of solid surfaces. The surface area that can be estimated using this method can be complicated at times.
Significance of physisorption and their characteristics in IIT JEE exam
Owing to the reduced weightage for the parts, this topic does have a weightage of around 3.33 percent in all years. This suggests that there will be 1 or 2 questions on this topic, each with a point value of 4 points.
FAQs
What is the relationship between physisorption and temperature?
Temperature and physisorption are inversely connected. The rate of physisorption reduces as the temperature rises.
In physisorption, what kind of forces occur between the adsorbate and the adsorbent?
Adsorption in which the force between the adsorbate and the adsorbent is a physical van der Waals force is known as physisorption. It's because the adsorbate and adsorbent have weak Van der Waals forces.
Is physical adsorption a natural phenomenon?
Physical adsorption, on the other hand, is non-specific in nature.
