Which of the following gas should have maximum value for `k_H`?

Options

A. He
B. `H_2`
C. `N_2`
D. `CO_2`

Answer

To determine which gas has the maximum value for Henry's law constant \( k_H \), we need to understand the relationship between \( k_H \) and the atomicity of the molecules involved.

**Step 1: Understand Henry's Law Constant \( k_H \)**
Henry's law states that the amount of gas that dissolves in a liquid at a given temperature is proportional to the partial pressure of that gas above the liquid. The constant \( k_H \) is a measure of this proportionality. It is known that \( k_H \) is inversely proportional to the atomicity of the gas molecules.

**Step 2: Identify the Gases and Their Atomicity**
We need to identify the atomicity of each gas listed in the options:
- Helium (He): Atomicity = 1 (monatomic)
- Hydrogen (H₂): Atomicity = 2 (diatomic)
- Nitrogen (N₂): Atomicity = 2 (diatomic)
- Carbon Dioxide (CO₂): Atomicity = 3 (triatomic)

**Step 3: Compare the Atomicities**
Now we compare the atomicities:
- Helium: 1
- Hydrogen: 2
- Nitrogen: 2
- Carbon Dioxide: 3

**Step 4: Determine the Maximum \( k_H \)**
Since \( k_H \) is inversely proportional to atomicity, the gas with the lowest atomicity will have the highest \( k_H \). In this case, helium has the lowest atomicity (1).

**Conclusion**
Therefore, the gas that should have the maximum value for \( k_H \) is helium.

**Final Answer:** Helium (He) has the maximum value for \( k_H \).

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