Question

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason $R$
Assertion A: Amongst $He, Ne, Ar$ and $Kr$; $1 g$ of activated charcoal adsorbs more of $Kr$
Reason R: The critical volume $V_c\left( cm ^3 mol ^{-1}\right)$ and critical pressure $P_e$ (atm) is highest for Krypton but the compressibility factor at critical point $Z_c$ is lowest for Krypton 
In the light of the above statements, choose the correct answer from the options given below

• A. Both $A$ and $R$ are true but $R$ is NOT the correct explanation of $A$
• B. Both $A$ and $R$ are true and $R$ is the correct explanation of $A$
• C. A is false but $R$ is true
• D. $A$ is true but $R$ is false

Hint:

The adsorption of gases on activated charcoal depends on molecular size and van der Waals forces, not directly on critical parameters like Vc,Pc, or Zc.

Answer 1

The Correct Option is D

Analysis of Assertion and Reason:

1. Assertion (A): Among the noble gases, Krypton (Kr) is adsorbed more by activated charcoal compared to He, Ne, and Ar. This is because the extent of adsorption increases with an increase in molecular size and van der Waals forces, both of which are higher for Krypton. Thus, Assertion (A) is true.
2. Reason (R): The given reason states that the critical volume (V_c) and critical pressure (P_c) are highest for Krypton, and the compressibility factor (Z_c) at the critical point is lowest. However, this is incorrect because Krypton does not have the highest V_c or P_c among noble gases, and Z_c is not a determining factor for adsorption. Therefore, Reason (R) is false.

Conclusion: Assertion (A) is true, but Reason (R) is false. The correct answer is 4.