Question

What is the molar solubility of Fe(oh)3 in a buffer solution with pH 8•20 KSP = 4•0 ×10∆-38

Answer 1

pH = 8.20

pH + pOH = 14. Solve for pOH.
pOH = -log(OH^-). Solve for (OH^-)
..................Fe(OH)3 ==> Fe^3+ + 3OH^-
Ksp = (Fe^3+)(OH^-)^3 = 4.0E-38
Plug in (OH^-), cube it, solve for (Fe^3+) = solubility Fe(OH)3 in moles/L.
Post your work if you get stuck.