van der Waal's equation is true for

Options

A. Ideal gas
B. Real gas
C. Gaseous substance
D. None of the above

Explanation

To determine for which gases Van der Waals' equation is applicable, we can follow these steps:

### Step 1: Understand the Van der Waals Equation
The Van der Waals equation is given by:
\[ \left( P + \frac{a n^2}{V^2} \right) (V - nb) = nRT \]
where:
- \( P \) = pressure of the gas
- \( n \) = number of moles of the gas
- \( V \) = volume of the gas
- \( a \) = Van der Waals constant related to the attractive forces between molecules
- \( b \) = Van der Waals constant related to the volume occupied by the gas molecules
- \( R \) = universal gas constant
- \( T \) = temperature

### Step 2: Identify Real Gases
The Van der Waals equation is specifically designed to correct the ideal gas law for real gases. Real gases do not behave ideally under all conditions due to:
- Intermolecular forces (attractive or repulsive)
- The finite volume occupied by gas molecules

### Step 3: Compare with Ideal Gas Behavior
In contrast, the ideal gas law is given by:
\[ PV = nRT \]
This equation assumes no intermolecular forces and that gas molecules occupy no volume. Therefore, the Van der Waals equation becomes necessary when dealing with real gases, especially at high pressures and low temperatures where deviations from ideal behavior are significant.

### Step 4: Conclusion
The Van der Waals equation is applicable for real gases, which exhibit non-ideal behavior due to molecular interactions and finite volume. Therefore, the correct answer to the question is that Van der Waals' equation is true for real gases.