Question

Identify the incorrect option from the following?

• A. Physical adsorption is multi-layer, non-directional and non- specific
• B. Chemisorption is very slow at ​low temperatures​
• C. Chemical adsorption increases ​with decrease in surface ​area of the adsorbent.
• D. Chemical adsorption is more stronger than physical adsorption

Answer 1

The correct option is C Chemical adsorption increases ​with decrease in surface ​area of the adsorbent.

Physisorption is the process of accumulation of a gas
on the surface of a solid on account of weak van der Waals’ forces.
Since it occurs through weak van der Waals' forces, the physical adsorption is non-specific, non-directional and multi-layer.

In chemisorption, gas molecules or atoms of the adsorbate are held to the solid surface of the adsorbent by the chemical bonds.​
Since, chemical bonds are stronger than van der Waals' force, chemical adsorption is stronger than physical adsorption.

Due to formation of chemical bonds, chemisorption is generally irreversible.
Although chemisorption is exothermic, it is very slow at low temperature because it requires high activation energy to form chemical bonds.

Like physisorption, chemisorption also increases ​with increase in surface ​area of the adsorbent.​

Hence, statements (a), (c) and (d) are correct and (b) is incorrect.