Question

The vander waals constants for gases A,B and C are as follows:
Gas $a/{dm}^{6}kPa{mol}^{-2}b/{dm}^3{mol}^{-1}$
A. 405.3 0.027
B. 1215.9 0.030
C. 607.95 0.032
Which gas has (i) the highest critical temperature (ii) the largest molecular volume, and (iii) most ideal behavior around STP?

Answer 1

Critical temperature = $T_c=\frac{8a}{27Rb}\propto \frac{a}{b}$

For $A\to \frac{a}{b}=\frac{405.3}{0.027}=15011.11$

For $B\Rightarrow \frac{a}{b}=\frac{\mathrm{1215.5.9}}{0.090}=40530$

For $C\to \frac{a}{b}=\frac{607.95}{0.032}=18988.43$

$\therefore$ The $T_c$ will be highest for B $V_e=3b\propto b$

$\therefore V_c$ will be highest for $e$

most ideal behaviour will be shown by that having last $a$

$\therefore$ it is $A$