Question

1 mole of a diatomic gas present in a 10 L vessel at a certain temperature exerts a pressure of 0.96 atm. Under similar conditions, an ideal gas exerts 1.0 atm pressure. If the volume of a gas molecule is negligible, then find the value of the van der Waals’ constant $‘a^{\prime }$ (in ${\text{atm L}}^2/{\text{mol}}^2$).

Answer 1

'b' is negligible $\therefore (P+\frac{a}{V_m^2})V_m=RT$
$\Rightarrow (P+\frac{a}{V_m^2})=\frac{RT}{V_m}=P_{ideal}$
$\Rightarrow 0.96+\frac{a}{V_m^2}=1$
$\Rightarrow \frac{a}{V_m^2}=0.04$
Now, $V_m=10L$
$\therefore a=0.04\times 100=4$