Q. At low pressure, the van der Waals’ equation is reduced to
A) $Z = \frac{pV_{m}}{RT} = 1 - \frac{ap}{RT}$
B) $Z = \frac{pV_{m}}{RT} = 1 + \frac{b}{RT}p$
C) $pV_{m} = RT$
D) $Z = \frac{pV_{m}}{RT} = 1 - \frac{a}{RT}$
Explanation
(d)
Van der Waals’ equation (at low pressure),
$\left\lbrack p + \frac{a}{V^{2}} \right\rbrack(V - b) = RT$
or $pV = RT + pb - \frac{a}{V} + \frac{ab}{V^{2}}$
or $\frac{pV_{m}}{RT} = 1 - \frac{a}{RT} = Z$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.