In: Chemistry
The complex ion Cu(NH3)42 is formed in a solution made of 0.0400 M Cu(NO3)2 and 0.400 M NH3. What are the concentrations of Cu2 , NH3, and Cu(NH3)42 at equilibrium? The formation constant*, Kf, of Cu(NH3)42 is 1.70 × 1013.
Cu^2+(aq) + 4NH3(aq) <---> Cu(NH3)4^2+(aq)
Kf, of Cu(NH3)42 is 1.70 × 10^13
Cu2+ + 4 NH3 -------> [Cu(NH3)42+]
I
0.0400
0.400
0.0
c
- 0.0400
-
(4*0.400)
0.0 400
E 0 0.24 0.0400
Thus at equilibrium concentration of [Cu2+]= 0
Cu2+ + 4 NH3
<--------> [Cu(NH3)4 2+]
I
0
0.
24
0.04
c
+x
+4x
-x
E
x
0.24
+4x
0.04-x
Kf= [Cu(NH3)4 2+] / [Cu2+][ NH3]^4
1.70 x 10^13 = 0.04-x / x ( 0.24+4x)^4
1.70 x 10^13 = 0.04/ x ( 0.24)^4 = 12.06/x
x =7.09* x 10^-13M
[Cu2+]= 7.09 x 10^-13 M
[NH3]= 0.24 +4x = 0.24
Cu(NH3)4 2+] = 0.04-x = 0.03999 or 0.04