equilibrium ion question

[haber101]

Calculate the milligrams of metallic ion that can remain at equilibrium in a solution of Fe(OH)3 having a [OH-] = 1.0 x 10-4 mol/L and Ksp = 6.0 x 10-38.

[PhaseShifter]

You're missing some important information, like the volume of solution.

It's possible to calculate the concentration of Fe3+ from that information, but not the mass.