64

32

28

21

$\mathrm{H}_2$

He

$\mathrm{CO}_2$

$\mathrm{NH}_3$

1

$1+\frac{R T}{P b}$

$1-\frac{R T}{P b}$

$1+\frac{P b}{R T}$

van der Waals' constants ' $a$ ' of $\mathrm{CO}_2$ and $\mathrm{NH}_3$ are greater than that of $\mathrm{N}_2$.

Van der Waals' constant ' $a$ ' of $\mathrm{CO}_2$ and $\mathrm{NH}_3$ are less than that of $\mathrm{N}_2$.

' $a$ ' $\left(\mathrm{NH}_3\right)>$ ' $a$ ' $\left(\mathrm{N}_2\right)$ but ' $a$ ' $\left(\mathrm{CO}_2\right)<$ ' $a$ ' $\left(\mathrm{N}_2\right)$

' $a$ ' $\left(\mathrm{NH}_3\right)<$ ' $a$ ' $\left(\mathrm{N}_2\right)$ but ' $a$ ' $\left(\mathrm{CO}_2\right)>$ ' $a$ ' $\left(\mathrm{N}_2\right)$