(Review complex formation before trying this.)

 

Concentrated NH4OH was added to 1.00 L of 0.200 M CuSO4 until [NH3] = 0.600.  All of the copper was in solution, mostly in the form of Cu(NH3)n2+ complexes.  What were the concentrations of the various copper species and how much NH4OH was added?  (Table  11.5 might prove useful.) (As short a question as this is, there are several steps involved.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Answers:(Revived...the species had inadvertently been reversed vs the answers.)

Cu2+ + 4 NH3 --> Cu(NH3)42+ Kf=1.1 X 10 12

(0.2-x)/(0.6+x)4(x) = 1.1 X 10 12

x = [Cu2+]/1M ~ 0.2/(0.6)4(1.1 X 10 12) = 1.4 X 10 -12

 

[Cu(NH3)42+] = 0.196 M

 

[Cu(NH3)32+] = 3.7 X 10-3 M

 

[Cu(NH3)22+] = 1.2 X 10-5 M

 

[Cu(NH3)2+] = 1.0 X 10-8 M

 

[Cu2+] = 1.4 X 10-12 M

 

Total NH3 = 0.600 free and 4(.200) bound to copper in various combinations = 1.40 moles