The compressibility factor for `H_2` and He is usually

Options

A. gt1
B. `=1`
C. lt1
D. Either of these

Answer

To determine the compressibility factor (Z) for Hydrogen (H₂) and Helium (He), we can follow these steps:

### Step 1: Understand the Compressibility Factor
The compressibility factor (Z) is a measure of how much a real gas deviates from ideal gas behavior. It is defined by the formula:
\[ Z = \frac{pV}{RT} \]
where:
- \( p \) = pressure of the gas
- \( V \) = volume of the gas
- \( R \) = universal gas constant
- \( T \) = temperature of the gas

### Step 2: Analyze the Nature of Hydrogen and Helium
Both Hydrogen and Helium are light gases with weak intermolecular forces. However, they primarily exhibit repulsive forces at short distances due to their low molecular weights and small atomic sizes.

### Step 3: Consider the Effect of Intermolecular Forces
In real gases, repulsive intermolecular forces cause the actual volume of the gas to be greater than the volume predicted by the ideal gas law. This means that for gases like H₂ and He, the compressibility factor will be greater than 1.

### Step 4: Conclusion
Since both Hydrogen and Helium exhibit repulsive forces, the compressibility factor for these gases will be:
\[ Z > 1 \]

Thus, the correct answer is that the compressibility factor for H₂ and He is greater than 1.

### Final Answer
The compressibility factor for Hydrogen (H₂) and Helium (He) is usually greater than 1.

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