0.6 mole of $\mathrm{PCl}_5, 0.3$ mole of $\mathrm{PCl}_3$ and 0.5 mole of $\mathrm{Cl}_2$ are taken

Question

0.6 mole of $\mathrm{PCl}_5, 0.3$ mole of $\mathrm{PCl}_3$ and 0.5 mole of $\mathrm{Cl}_2$ are taken in a 1 L flask to obtain the following equilibrium : 
$ \mathrm{PCl}_{5(g)} \rightleftharpoons \mathrm{PCl}_{3(g)}+\mathrm{Cl}_{2(g)} $
 If the equilibrium constant $K_c$ for the reaction is 0.2 , predict the direction of the reaction.

Professor PC Thomas Classes · Answer

(b) : $\mathrm{PCl}_{5(g)} ightleftharpoons \mathrm{PCl}_{3(g)}+\mathrm{Cl}_{2(g)}$ 
$ Q_c=\frac{0.5 	imes 0.3}{0.6}=0.25, K_c=0.2 $
 Since, $Q_c>K_c$ reaction will proceed in backward direction.