Aqueous sodium chloride?An everyday example of a system that is at dynamic equilibrium is the dissociation of sodium chloride in water. In this simple reaction, salt (NaCl) can be added to water. It will begin dissolving until the solution in completely saturated. When the solution is saturated, and more NaCl is added, there will be visible salt crystals seeming to be at rest at the bottom of the aqueous solution. These salt crystals are not at rest; in fact they are actually continuously dissociating and reforming. Because this reaction is continuously happening in both forward and reverse directions, it is said to be at dynamic equilibrium. This reaction is represented by the following equation:
NaCl(s) <----> NaCl(aq) |