• # question_answer At low pressures, the van der Waals' equation is written as:$\left( p+\frac{a}{{{V}^{2}}} \right)V=RT$. The compressibility factor is then equal to A)  $\left( 1-\frac{a}{RTV} \right)$                     B)  $\left( 1-\frac{RTV}{a} \right)$ C) $\left( 1+\frac{a}{RTV} \right)$                    D)  $\left( 1+\frac{RTV}{a} \right)$

$\because$    $\left( p+\frac{a}{{{V}^{2}}} \right)V=RT$ or         $pV+\frac{a}{V}=RT$ or         $pV=RT-\frac{a}{V}$ or         $Z=1-\frac{a}{RTV}$ $\therefore$    $Z<1$ always