Question

Which of the following terms of Vander Waals equation of state for a non-ideal gas accounts for intermolecular attraction forces?

• A. \(RT\)
• B. \(\left(P+\frac{a}{V^2}\right)\)
• C. \((V-b)\)
• D. \(\frac{1}{RT}\)

Hint:

In Vander Waals equation, \(a\) corrects pressure due to attractive forces, while \(b\) corrects volume due to finite molecular size.

Answer 1

The Correct Option is B

The Vander Waals equation for a real gas is: \[ \left(P+\frac{a}{V^2}\right)(V-b)=RT. \] For one mole of gas, \(a\) and \(b\) are Vander Waals constants. The term: \[ \frac{a}{V^2} \] is the pressure correction term. This correction is added because real gas molecules attract each other. Due to intermolecular attraction, the observed pressure of a real gas is less than the ideal pressure. So, the pressure is corrected as: \[ P+\frac{a}{V^2}. \] The term: \[ (V-b) \] is the volume correction due to finite molecular size. Therefore, the term accounting for intermolecular attraction forces is: \[ \left(P+\frac{a}{V^2}\right). \]