HELP w/an AP Chemistry question.

Test Preparation
1

<p>I have a Ksp question that I don’t know how to deal with. It involves the ksp of a metal hydroxides (I think those involve special cases): </p>

<p>The ksp of Fe(OH)3 = 4 x 10^(-38). What is its molar solubility at </p>

<li>pH = 10</li>
<li>pH = 4</li>
</ol>

<p>I started with Fe(OH)3 <=> Fe^3+ + 3OH-
I could use the ksp = x(3x)^3 formula for concentrations, but i don’t think that that is correct for metal hydroxides. Can anyone help please?</p>

2

<p>If the pH is fixed at a certain value, then that fixes [OH-] as well. So for 1) you have [OH-] = 10^(14-10) = 10^-4 and for 2) you have [OH-] = 10^-10. Then solve Ksp = x (10^-4)^3 and Ksp = x (10^-10)^3 for x.</p>