What is the concentration of Cu2+ in a solution that is 0.10 M Cu(NH3)4^2+? (Kf = 1.2 x 10^12)

Question

The answer is 8.0 x 10^-4

How do I solve the problem to get the answer

Answer 1

Write the equation and set up an ICE chart.
.........Cu^2+ + 4NH3 ==> Cu(NH3)4^2+
I........0........0.........0.1
C........x........4x........-x
E........x.......4x.........0.1-x

Kf = 1.2E12 = [Cu(NH3)4^2+]/(x)(4x)^4
Solve for x.
8E-4 M is correct.