Question

Assertion: Physical absorption of molecules takes place on surface only.
Reason: In this process, the bonds of the absorbed molecules are broken.
(A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
(B) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
(C) Assertion is correct but Reason is incorrect
(D) Both Assertion and Reason are incorrect

Answer 1

To solve this question, we need to look at the basic definitions of absorption and adsorption. After we get to know the definitions of both of these terms, we can compare it with the assertion and the reason. In physisorption or physical adsorption, the bonds formed are Vander Waal interactions only.

Complete Step By Step Solution
First of all, we will look at the basic definition and few properties of absorption as well as adsorption.
Molecular system assimilation throughout the bulk of the solid or liquid medium is referred to as absorption. It is a bulk phenomenon. It is an endothermic process and the temperature plays no role in the process of absorption. It occurs at a uniform rate and is constant throughout the medium.
Adsorption is a method involving the accumulation of a substance at a higher concentration on the surface in molecular species. It is a surface phenomenon. It is an exothermic process and the process of adsorption is affected by low temperature. It increases steadily and achieves equilibrium. The concentration of adsorbent at the bottom varies from that in bulk.
Now,
By looking at these properties, we can say that absorption is a bulk phenomenon and adsorption is a surface phenomenon. So, absorption will not only occur at the surface of the substance, rather it will be uniformly distributed throughout the substance.
So, our assertion is wrong.
Also,
Since, absorption is a physical phenomenon, the chemical properties of the substance cannot change under ordinary conditions. The absorbed molecules cannot be broken as stated in the reason.
So, our reason is also wrong.
Hence, the correct option is (D.)

Note
Absorption is a separate mechanism from adsorption because the length, not the air, is soaked up by molecules undergoing absorption. Adsorption is based on the surface where an adsorbate film is developed on the surface, and the complete volume of the absorbing agent is included in the absorption. It should be noted here that, at a given temperature and pressure, the greater the adsorbent surface area, the greater the degree of adsorption.