Use the data in this table to calculate the solubility of each sparingly soluble substance in its respective solution.

Question

(a) silver bromide in 0.066 M NaBr(aq)
mol · L-1
I know how to do this one, found it to be 1.167E-11 which is correct.

(b) nickel(II) hydroxide in 0.256 M NiSO4(aq); For the purpose of this calculation, ignore the autoprotolysis of water.
mol · L-1
Ksp for Ni(OH)2 is 6.5E-18

Here's what I started doing:
NiSO4 -->NI^+ + SO4^-
Ksp = [Ni+][SO4-]

Ni(OH)2--> Ni^2+ + 2OH^-
Ksp = [Ni^2+][OH-]^2

so... [OH-]^2 = Ksp of [Ni^2+][OH-}^2 over [Ni+] from the NiSO4

but I'm not sure what to do because the first compound has Ni+ and the second has Ni 2+ ..

Addendum: What i've tried doing is...

[OH-]^2= 6.5E-18 / .256 = 2.54E-17 and then finding the square root of that, which is 5.04E-9. this is what makes most sense to me...but is apparently incorrect...

Answer 1

Answered below.