What is the formula for the ksp of fe(oh)3 ? use the equation mc011-1.jpg
ksp = [fe3+ ][oh- ]
ksp = [fe3+ ]3 [oh- ]
ksp = [fe3+ ][oh- ]3
ksp = 3[fe3+ ][oh- ]

Ksp, the product of solubility constant is given by the product of the concentrations in the equilibrium of the species on the right hand of the equillibrium reaction, each raised to a power that is its coeffiicient in the equillibrium reaction.

So you must start by writing the equilibrium reaction:

Fe(OH)3 (s) > Fe(3+) aq  +   3 (OH-) aq

Now you can state the formula for the Ksp

=> Ksp = [Fe (3+) aq] [OH-]^3

So, the answer is the third option of the list.