Question

The vapour density of equilibrium mixture for $N_2{O}_4\left(g\right)\rightleftharpoons 2N{O}_2\left(g\right)$ is 28.75 at 1 atm. This mixture is allowed to diffuse out for 10 seconds. Calculate the $K_p$ of the reaction after 10 seconds.

Answer 1

$V.D\left(d\right)=28.75$
$D=\frac{92}{2}=46$
$\alpha =\frac{D-d}{(n-1)d}=\frac{46-28.75}{(2-1)28.75}=0.6$
Now,
$\begin{array}{cccc}{N}_2{O}_4& \rightleftharpoons & 2N{O}_2& \\ 1& & 0& \text{(initial)}\\ 0.4& & 1.2& \text{(At Equilibrium)}\end{array}$
At equilibrium,
$n=1.2+0.4=1.6K_p=\frac{P_{N{O}_2}^2}{P_{N_2{O}_4}}=\frac{{\left(\frac{1.2}{1.6}\right)}^2}{\left(\frac{0.4}{1.6}\right)}=2.25K_p\text{does not change}$