Question

Using Van der Waals equation $[P+\frac{a}{V^2}](V-b)=RT$, the term that accounts for intermolecular forces in the Van der Waals equation for non-ideal gas is______

• A. $RT$
• B. $V-b$
• C. $[P+\frac{a}{V^2}]$
• D. $R{T}^{-1}$

Answer 1

The correct option is C $[P+\frac{a}{V^2}]$

Van der Walls noted that the total force of attraction on any molecule about to hit a wall is proportional to the concentration of neighbouring molecules, nN. However, the number of molecules about to hit the wall per unit wall area is also proportional to the concentration n/V. Therefore, the force per unit wall area, or pressure, is reduced from that assumed in the ideal gas wall by a factor proportional to $n^2/V^2$ . Letting a be the proportionality constant, we can write

$P\left(actual\right)=P\left(ideal\right)-n^{2}a/V^2$

$P\left(ideal\right)=P\left(actual\right)+n^{2}a/V^2$