For the reaction
Zn(OH)2(s)+4CN-(aq)->Zn(CN)4 2-(aq)+2OH-(aq)
find [CN-] when 8.5 g of Zn(OH)2 are dissolved in 1.00 L of solution.
Hmmm.
The Ksp for this reaction is in the order of E18, so you can assume the reaction goes to completion fully.
If it goes to full completion, then the amount of CN- in the reaction depends entirely on how much was in the solution in the beginning. You know you used 4 times the amount of moles of Zn(OH)2 (which you can calculate). How much left? depends on how much you started with.