van der Waal's equation explains the behaviour of

Options

A. Elementary gases
B. Real gases
C. Ideal gases
D. Mixture of ideal and real gases

Explanation

### Step-by-Step Solution:

1. **Understanding Ideal Gas Behavior**:
- The ideal gas equation is given by \( PV = nRT \), where \( P \) is pressure, \( V \) is volume, \( n \) is the number of moles, \( R \) is the universal gas constant, and \( T \) is temperature.
- In this equation, it is assumed that the volume of gas particles is negligible and that there are no intermolecular forces acting between them.

2. **Introduction to Real Gases**:
- Real gases do not behave perfectly as ideal gases under all conditions. They exhibit behaviors that deviate from the ideal gas law, especially at high pressures and low temperatures.

3. **Van der Waals Equation**:
- To account for the behavior of real gases, Van der Waals modified the ideal gas equation. The Van der Waals equation is expressed as:
\[ \left( P + \frac{a n^2}{V^2} \right) (V - nb) = nRT \]
- Here, \( a \) and \( b \) are the Van der Waals constants that account for the attractive forces between gas molecules and the volume occupied by the gas molecules, respectively.

4. **Pressure Correction**:
- The term \( \frac{a n^2}{V^2} \) represents the pressure correction due to intermolecular attractions. This term increases the pressure in the equation to account for the attractive forces that reduce the pressure exerted by the gas.

5. **Volume Correction**:
- The term \( nb \) represents the volume correction, which accounts for the finite volume occupied by the gas molecules. This correction reduces the volume available for the gas to move, as it considers the space occupied by the gas particles themselves.

6. **Conclusion**:
- Van der Waals equation effectively explains the behavior of real gases by incorporating corrections for intermolecular forces and the volume of gas particles. This makes it a more accurate representation of gas behavior under various conditions compared to the ideal gas law.

### Final Answer:
Van der Waals equation explains the behavior of real gases.