So if we were to write the equilibrium constant expression it would be this concentration divided by this concentration and we'll see why that's important in a second. 1st, let's review exactly what happens in this setup. Well, this is the more dilute solution. Initially, we have very little aqueous cu two plus ions dissolved in our solution but as that reaction continues, this metal bar releases more of the copper ions into solution increasing the solution, making more concentrated. Likewise, this acreage copper is taken up by the metal bar because when electrons travel from this electrode to this electrode they react to form copper solid so this becomes more diluted or less concentrated. Eventually, when the two concentrations equal our reaction will stop because our cell voltage will be zero.