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, `1g` of activated charcoal adsorbs more of Kr
Reason R: The critical volume `V_(c)(cm^(3)mol^(-1))` and critical pressure `P_(c)(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

Options

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

Answer

To solve the given question, we need to analyze both the Assertion (A) and the Reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that among the gases He (Helium), Ne (Neon), Ar (Argon), and Kr (Krypton), 1g of activated charcoal adsorbs more of Kr.
- Adsorption is generally influenced by the molecular weight of the gas. He has the lowest molecular weight, followed by Ne, Ar, and Kr, which has the highest molecular weight.
- Since adsorption increases with molecular weight for non-polar gases like noble gases, it is reasonable to conclude that activated charcoal would adsorb more of Kr compared to the others.

**Conclusion for Assertion (A)**: The assertion is **True**.

2. **Understanding the Reason (R)**:
- The reason states that the critical volume (Vc) and critical pressure (Pc) are highest for Krypton, but the compressibility factor at the critical point (Zc) is lowest for Krypton.
- It is true that Krypton has a higher critical volume and critical pressure compared to He, Ne, and Ar.
- However, the compressibility factor (Z) at the critical point for real gases is not necessarily lowest for Krypton. In fact, for real gases, the compressibility factor at the critical point is typically around 3/8 for many gases, including noble gases.
- Therefore, the statement regarding the compressibility factor being lowest for Krypton is incorrect.

**Conclusion for Reason (R)**: The reason is **False**.

3. **Final Evaluation**:
- Since the assertion is true and the reason is false, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- The correct option is **4**: Assertion is true but Reason is false.