.......Mg(OH)2 ==> Mg^2+ + 2OH^-
I......solid........0........0
C......solid........x........2x
E......solid........x........2x
So Ksp = 1.2E-10
You want solubility Mg(OH)2 to be 2.51E-8M = (Mg^2+) = x in the above equation.
Plug those values into Ksp expression and solve for OH^-, then convert to pH.
It is possible to manipulate the solubility of some compounds through pH adjustments. What is the appropriate pH that will yield a Molar solubility for Mg(OH)2 of 2.51 x 10-8? The Ksp for Mg(OH)2 is 1.2 x 10-11. (Hint: you may assume the concentration of hydroxide is constant as the solute dissolves, since so little dissolves. Also, it is required to solve for pOH in this problem and then convert to pH.)
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