According to Le Chatelier's Principle: What happens when you add DIFFERENT species to the equilibrium?

Question

Wyatt Atkins · Accepted Answer

Le Chatelier's principle applies to equilibrium concentrations in specific equilibria. Addition of different species that affect these equilibrium concentrations, will change the equilibria accordingly.

Consider the solution behaviour of a sparingly soluble or insoluble salt at equilibrium, say #AgCl#. We write #AgCl(s) rightleftharpoons Ag^+ + Cl^- ##(i)# To describe this reaction, we write #K_(sp) = [Ag^+][Cl^-]#. Should we add aqueous ammonia we will reduce the #[Ag^+]# value because of the following competing equiibrium: #Ag^+ + 2NH_3 rightleftharpoons [Ag(NH_3)_2]^+##(ii)# More silver ion, #[Ag^+]#, will enter solution because it can be complexed by the ammonia. To give an answer in terms of Le Chatelier's principle, because we reduce #[Ag^+]# in equilibrium (i), we can drive the equilibrium to the right hand side. On the other hand, for equilibrium (ii), if we reduce #[NH_3]#, say by increasing the #pH# to form #NH_4^+#, we would drive the equilibrium to the left. Of course, we are dealing with competing equilibria, that may be difficult to calculate.

Cameron Andrews · Answer

undefined When you add different species to an equilibrium system, Le Chatelier's Principle states that the system will adjust to counteract the disturbance. If you add a reactant, the equilibrium will shift to favor the formation of products, and if you add a product, the equilibrium will shift to favor the formation of reactants.