Question

Calculate the solubility (in grams per 1.00 102 mL of solution) of magnesium hydroxide in a solution buffered at pH = 9. Enter your answer to 2 significant figures.) Ksp = 2.06e-13

Answer 1

pH = 9 means pOH = 5 and (OH^-) = 1E-5

........Mg(OH)2 ==> Mg^2+ + 2OH^-
Ksp = (Mg^+)(OH^-) = 2.06E-13
Substitute 1E-5 for OH and solve for Mg. That gives solubility in mols/L. Convert to mols/100 mL, the convert mols to grams.

Answer 2

does the 2 in front of the OH^- get corporate into the Ksp making it (OH)^2??

Answer 3

Yes, the OH^- is squared.
2.06E-13 = (Mg^2+)(1E-5)^2
Solve for Mg^2+. I see I made a typo and omitted the square of OH on my first response. It is
Ksp = (Mg^2+)(OH^-)^2 etc. Sorry about that.