[JJ]

I am asked to use the solubility product for Fe(OH)₃ to calculate the pH at which it will begin to precipitate from .20M Fe³⁺ solution.

Do I need to use an ICE box to calculate this?
I have two K_sp values but use the one given in my lab manual (since this is for lab and not lecture) = 2.6E-39
Now, I know pH=-log[H⁺] so, I'm assuming I need to write/balance an equation and find the molarity of the OH^- and then I can find the pH....

Thanks so much,
JJ

[Borek]

From Ksp and known concentration of Fe³⁺ calculate concentration of OH^- needed for precipitation to start, then convert OH^- to pH. That's all.