One way of writing the equation of state for real gases is
`PV=RT[1+(B)/(V)+….]`
where `B` is a constant. Derive an approximate expression for `B` in terms of the van der Waals constants `a` and `b`.

Explanation

To derive an approximate expression for the constant \( B \) in terms of the van der Waals constants \( a \) and \( b \), we start from the van der Waals equation for real gases, which is given by:

\[ \left( P + \frac{a}{V^2} \right)(V - b) = RT \]

1. **Rearranging the van der Waals equation**:
We can expand this equation to express \( P \) in terms of \( V \):
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