Solubility in g/L of zinc hydroxide with pH of 8

[Scatteredheroes]

Homework Statement

Zinc hydroxide has the chemical formula of Zn(OH)2. It has a very low solubility. What is the solubility in g/L of Zinc Hydroxide in a solution with a pH of 8?

Homework Equations

zinc hydroxide formula
14-pH = pOH[/B]

The Attempt at a Solution

10^-6 (the pOH) gives me the concentration of the OH- ion.

That gives me the unknown in mols/L.

I multiply it by the molar mass, but it's wrong. What am I doing wrong?

 

[SteamKing]

Why don't you show all your calculations?

How many OH^- radicals are there in each molecule of Zn(OH)₂ ?

 

[Borek]

OH^- in the solution are NOT from the dissolved Zn(OH)₂.

I would check what is the Ksp of the zinc hydroxide and use this number in the calculations.

Sadly, the question is rather ambiguous. The final result is most likely different depending on whether the pH is buffered at 8, or is 8 initially (and there is no buffering effect). Hard to say what they mean.

 

[epenguin]

I would read that as somehow maintained at pH 8 by some means, of which the most obvious is buffering (can also be done by e.g. An automatic titrator). Unfortunately you wil meet this sort of 'lab slang' often enough. But there is still not enough information and K_sp is needed.