Question

Gases $X,Y,Z,P$ and $Q$ have the van der Waals' constant ${}^{\prime }{a}^{\prime }$ and ${}^{\prime }{b}^{\prime }$ (in CGS units) as shown below:

	$X$	$Y$	$Z$	$P$	$Q$
$a$	$6$	$6$	$20$	$0.05$	$30$
$b$	$0.025$	$0.15$	$0.1$	$0.02$	$0.2$

The gas with the highest critical temperature is:

• A. $P$
• B. $Q$
• C. $Y$
• D. $Z$
• E. $X$

Answer 1

The correct option is E $X$

Critical temperature, $T_c=\frac{8a}{27Rb}$
$\therefore$ Grater is the value of $\left(a/b\right)$, more is the critical temperature of gas.
For gas $X,T_c$ will be maximum.
$T_c=\frac{8a}{27Rb}$
$\frac{a}{b}$ for $X=\frac{6}{0.025}=240$; for all gases, $\left(\frac{a}{b}\right)$ is lesser.