Chem
posted by Kim .
The question is;
About Fe+2 concentration will Fe(OH)2 precipitate from a buffer solution that has a PH = 9.29? The Ksp of Fe(OH)2 is 4.87x10^17
So here is what I did,
Ksp = (x) (2x)^2 = 4x^3
4.87x10^17 = 4x^3
x = 2.30x10^6
I don't know what do I have to do
after this.
Plz help me!

You had the right idea but where is the pH 9.29 part? And there must be a concn Fe^+2 in there somewhere.
Remember talking about Qsp?
Convert pH = 9.29 to OH^, then multiply
Qsp = (Fe^+2)(OH^)^2
Now compare Qsp with Ksp and you will know if a ppt occurs. Again, you must have Fe^+2 concn in the problem?