Question

Which of the following is/are application(s) of adsorption?

• A. De-ionization of water
• B. Gas masks
• C. Hygroscopic nature of $CaC{l}_2$
• D. Heterogeneous catalysis

Answer 1

Answer: (A), (B), (D)

The correct options are
A De-ionization of water
B Gas masks
D Heterogeneous catalysis

Adsorption :

The phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting into a higher concentration of the molecules on the surface is called adsorption. As a result of adsorption, there is a decrease of surface energy. The process of removal of an adsorbed substance from the surface on which it is adsorbed is called desorption. It is the reverse of adsorption and can be brought about by heating or by reducing the pressure.

Adsorption finds extensive applications both in research laboratory and in industry. A few applications are discussed below:
In gas masks:
All gas masks are devices containing suitable adsorbent so that the poisonous gases present in the atmosphere are preferentially adsorbed and the air for breathing is purified.
In heterogeneous catalysis:
The action of certain solids as catalysts is best explained in terms of adsorption. The theory is called adsorption theory. According to this theory, the gaseous reactants are adsorbed on the surface of the solid catalyst. As a result, the concentration of the reactants increases on the surface and hence, the rate of reaction increases. The theory is also able to explain the greater efficiency of the catalyst in the finely divided state, the action of catalyst promoters and poisons.
In softening of hard water (De-ionization of water):
The use of ion exchangers for softening of hard water is based upon the principle of competing adsorption just as in chromatography. Hygroscopic nature of $CaC{l}_2$ is not related to adsorption.