Question

Assertion: For adsorption $\Delta G,\Delta S{\text{ and }}\Delta {\text{H}}$ all have negative values.
Reason: Adsorption is a spontaneous process accompanied by a decrease in randomness.
A. If both (A) and (R) is the correct explanation of (A)
B. If both (A) and (R) are true, but (R) is not the correct explanation of (A)
C. If (A) is correct, but (R) is incorrect.
D. If (A) and (R) are both incorrect.

Answer 1

In the above question the values $\Delta G$ stand for Gibbs free energy, $\Delta S$ stands for entropy change, $\Delta H$ stands for enthalpy change which is all negative values. One can analyze these values by considering a relative equation and find out the correct option.

Complete step by step answer:
-First of all let's learn the concept of adsorption where the process leads to a decrease in the residual forces which are present on the surface of the adsorbent. This makes the decrease in the surface energy of the adsorbent molecule. Hence the adsorption reaction is always an exothermic process.
- Now let's analyze a relative equation which is the equation for Gibbs free energy as follows,
$\Delta G = \Delta H - T\Delta S$
In the above equation, the value of $\Delta H$ will be negative as the adsorption reaction is an exothermic reaction. The negative value sign before the entropy change i.e. $\Delta S$ shows that the $\Delta S$ value is negative. As the values of $\Delta S$ and $\Delta H$ are negative the value of $\Delta G$ will also be negative. Hence, the statement of assertion which states for adsorption $\Delta G,\Delta S{\text{ and }}\Delta {\text{H}}$ all have negative values is the correct statement.
-The exothermic reactions are spontaneous hence, adsorption is a spontaneous reaction. The randomness of the overall process decreases due to the presence of a force of attraction between adsorbent and adsorbate due to which the gas molecules stick to the surface.
- Therefore, the assertion and the reason both are a correct and correct explanation of assertion which shows option A as the correct choice.
So, the correct answer is “Option A”.

Note: : Adsorption and absorption are both different concepts were in absorption the fluid or material which is adsorbate gets permeate or absorbed in the solid or liquid which is adsorbent and in adsorption, there is just a deposition of a layer on the surface of the adsorbent. The concept of adsorption in the case of proteins is of great biological importance as protein is in contact with blood or body fluids get adsorbed and utilized for further biological processes.