Question

Does the chemical adsorption increase or decrease when the surface area of the adsorbent increases?

Answer 1

Part 1: Adsorption: In adsorption, the substance whose molecules get adsorbed at the surface is called the adsorbate. The substance on whose surface the process takes place is called the adsorbent.

• Adsorbate: Substance that is deposited on the surface of another substance. For example, ${\mathrm{H}}_2$, ${\mathrm{N}}_2$ and ${\mathrm{O}}_2$ gases.
• Adsorbent: Surface of a substance on which adsorbate adsorbs. For example, Charcoal, Silica gel, and alumina.

Part 2: Chemical adsorption :

Chemical adsorption occurs when the adsorbate molecule is held on the adsorbent surface by chemical forces as short covalent chemical bonding occurs by sharing electrons.

Characteristics of chemical adsorption:

1. This type of adsorption is caused by chemical forces.
2. It is a very strong process.
3. This type of adsorption is almost a single-layered phenomenon.
4. Chemisorption is highly specific and takes place at reaction centres on the adsorbent.
5. Surface area, temperature, and nature of adsorbate effects chemisorption.

• With the increase in surface area of adsorbent, chemical adsorption increases.
• If the adsorbent surface is more fine or rough, the surface area will be greater.
• This is because when we increase the surface area there is more number of adsorbing sites, hence the adsorption will be greater.