Following two equilibrium is simultaneously established in a container

$\begin{array}{r}{\mathrm{PCl}}_5\left(g\right)\rightleftharpoons {\mathrm{PCl}}_3\left(g\right)+{\mathrm{Cl}}_2\left(g\right)\\ \mathrm{CO}\left(g\right)+{\mathrm{Cl}}_2\left(g\right)\rightleftharpoons {\mathrm{COCl}}_2\left(g\right)\end{array}$

If some Ni(s) is introduced in the container forming $\mathrm{Ni}\left(\mathrm{CO}{)}_4\right(\mathrm{g})$ then at new equilibrium :

A reduction in product concentration favours the forward reaction. The rate of reverse reaction will reduce quickly, then gradually increase until equilibrium is restored. Simultaneously, the forward response rate will steadily decrease.