Tue 3 Aug, 2010 09:58 pm
A test for completeness of electrodeposition of Cu from a solution of Cu2+(aq) is to add NH3(aq). A blue color signifies the formation of the complex ion [Cu(NH3)2]2+ (Kf = 1.1x10^13). 250.0 mL of 0.1000 M CuSO4(aq) is electrolyzed with a 3.512 A current for 1368 s. A sufficient quantity of NH3(aq) is added to complex any remaining Cu2+ and to maintain a free [NH3] = 0.10 M. If [Cu(NH3)4]2+ is detectable at concentrations as low as 1x10^-5 M, would you expect the blue color to form in this case? 1 faraday = 96485 C/1 mol electrons.