Chemistry - Chemical Equilibrium Question with Solution | TestHub

Degree of dissociation=0.4

$\begin{array}{l}{\text{PCl}}_5\rightleftharpoons {\text{PCl}}_3+{\text{Cl}}_2\\ \text{a}(1-\text{x})\text{a}\text{x}\text{a}\text{x}\end{array}$

$\text{a}=2,\text{x}=0.4,\text{V}=2$

$\left[\mathrm{\text{P}}\mathrm{\text{C}}{\mathrm{\text{l}}}_5\right]=\frac{2(1-0.4)}{2}=0.6$mol/L

$\left[\mathrm{\text{P}}\mathrm{\text{C}}{\mathrm{\text{l}}}_3\right]=\frac{2\times 0.4}{2}=0.4$mol/L

$\left[\mathrm{\text{C}}{\mathrm{\text{l}}}_2\right]=\frac{2\times 0.4}{2}=0.4$mol/L

$\therefore$${\text{K}}_{\text{c}}=\frac{\left[\mathrm{\text{P}}\mathrm{\text{C}}{\mathrm{\text{l}}}_3\right]\left[\mathrm{\text{C}}{\mathrm{\text{l}}}_2\right]}{\left[\mathrm{\text{P}}\mathrm{\text{C}}{\mathrm{\text{l}}}_5\right]}$

$=\frac{0.4\times 0.4}{0.6}=0.267$