Show that the excluded volume is four times the actual volume of a molecule.

Explanation

To show that the excluded volume is four times the actual volume of a molecule, we can follow these steps:

### Step 1: Understand the Van der Waals Equation
The Van der Waals equation is given by:
\[ p + \frac{a n^2}{V^2} (V - nb) = nRT \]
In this equation, \( b \) represents the excluded volume for one mole of gas.

### Step 2: Define the Excluded Volume
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