Adsorption
Chapter Name : Surface Chemistry |
Sub Topic Code : 102_12_05_02_01 |
Topic Name : Adsorption |
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Sub Topic Name : Introduction |
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Introduction
The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption.
Pre-Requisites:
Adsorption, adsorbate, adsorbent
Activity:
The air becomes dry in the presence of silica gel because the water molecules get adsorbed on the surface of the gel.
Real Life Question:
The air becomes dry in the presence of silica gel. Why?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Adsorption | The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption. |
| Adsorbate | The molecular species or substance, which concentrates or accumulates at the surface, is termed as adsorbate. |
| Adsorbent | The material on the surface of which the adsorption takes place is called adsorbent. |
| Desorption | The process of removing an adsorbed substance from a surface on which it is adsorbed is called desorption. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Powdered charcoal, closed vessel | If a gas like O2, H2, CO, Cl2, NH3 or SO2 is taken in a closed vessel containing powdered charcoal, it is observed that the pressure of the gas in the enclosed vessel decreases. The gas molecules concentrate at the surface of the charcoal, i.e., gases are adsorbed at the surface. |
Real life uses :
Adsorption is effective for purifications.
Places to visit :
Chemistry lab
Practical examples around us
| Examples | Explainations |
|---|---|
| Charcoal action | Aqueous solution of raw sugar, when passed over beds of animal charcoal, becomes colourless as the colouring substances are adsorbed by the charcoal. |
What you learn in Theory:
The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption.
What you learn in Practice:
Adsorption is essentially a surface phenomenon. Solids, particularly in finely divided state, have large surface area and therefore, charcoal, silica gel, alumina gel, clay, colloids, metals in finely divided state, etc. act as good adsorbents.