Which statement(s) about the behaviour of a real gas is (are) wrong?

Options

A. A gas exerts more pressure compared to an ideal gas
B. A gas can be compressed more compared to an ideal gas
C. A gas with high value of van der Waals constant, a, is highly liquefiable
D. `H_(2)` and He are less compressible compared to an ideal gas at ordinary temperature

Answer

To determine which statements about the behavior of a real gas are wrong, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding Real vs. Ideal Gas Behavior**:
- An ideal gas follows the ideal gas law (PV = nRT) perfectly under all conditions, while real gases deviate from this behavior due to intermolecular forces and the volume occupied by gas particles.

2. **Analyzing Option 1**:
- **Statement**: A gas exerts more pressure as compared to an ideal gas.
- **Evaluation**: This statement is incorrect. Real gases generally exert less pressure than ideal gases at the same temperature and volume due to intermolecular attractions. Therefore, this statement is wrong.

3. **Analyzing Option 2**:
- **Statement**: The volume of the gas is less than the ideal gas.
- **Evaluation**: This statement is also incorrect. The volume occupied by a real gas is typically greater than the volume predicted by the ideal gas law because real gas particles occupy space and experience intermolecular forces. Hence, this statement is wrong.

4. **Analyzing Option 3**:
- **Statement**: A gas with a high value of the van der Waals constant 'a' is highly liquefiable.
- **Evaluation**: This statement is correct. A higher 'a' value indicates stronger intermolecular forces, which makes it easier for the gas to condense into a liquid. Thus, this statement is true.

5. **Analyzing Option 4**:
- **Statement**: H2 and helium are less compressible compared to an ideal gas at ordinary temperature.
- **Evaluation**: This statement is correct. Hydrogen and helium are light gases and have a compressibility factor greater than 1, indicating they are less compressible than ideal gases under ordinary conditions. Therefore, this statement is true.

### Conclusion:
The wrong statements about the behavior of a real gas are:
- Option 1: A gas exerts more pressure as compared to an ideal gas.
- Option 2: The volume of the gas is less than the ideal gas.