Q. The van der Waals’ equation for a real gas is given by the formula $\left( p + \frac{n^{2}a}{V^{2}} \right)(V - nb) = nRT,\ where\ p,\ V,\ T\ and\ n$ are the pressure, volume, temperature and the number of moles of the gas. Which one is the correct interpretation for the parameter $a?$
A) The parameter $a$ accounts for the finite size of the molecule, not included temperature in the ideal gas law.
B) The parameter $a$ accounts for the shape of gas phase molecules.
C) The parameter $a$ accounts for intermolecular interaction’s present in the molecule.
D) The parameter $a$ has no physical significance and van der Waals’ introduced it as a numerical correction factor only.
Explanation
(c)
In van der Waals’ equation
$\left\lbrack p + \frac{n^{2}a}{V^{2}} \right\rbrack\ (V–nb) = nRT$
Where, $p = pressure,\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ V = volume$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ T = temperature,\ \ \ \ \ \ \ \ n = moles\ of\ the\ gas$
and parameter $a$ accounts for intermolecular interactions present in the molecule.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.