Calculate the solubility (in grams per 1.00×102mL of solution) of magnesium hydroxide in a solution buffered at pH = 12
I got the answer correct for this, it being: S1 =
1.2×10−8 g/(1.00×102mL)
But I can't figure out the follow up question: How does this compare to the solubility of Mg(OH)2 in pure water?

Question

Calculate the solubility (in grams per 1.00×102mL of solution) of magnesium hydroxide in a solution buffered at pH = 12
I got the answer correct for this, it being: S1 = 	
1.2×10−8 g/(1.00×102mL)  
But I can't figure out the follow up question: How does this compare to the solubility of Mg(OH)2 in pure water?

aaronq · Answer

What did you use to find the first part?

you may want to use the fact that $[OH^-]$ is different at the 2 pH's.