Given: A magnesium hydroxide solution is prepared by adding 12.00 g of magnesium hydroxide to a volumetric flask and bringing the final volume to 1.15 L by adding water buffered at a pH of 7.0.

Required:

A. [Molar] concentration of magnesium in this solution. Use pK_SP = 11.25 to find K_SP

B. Repeat Part A, except, use a solution pH of 12. You do not need to repeat the parts of the problem that are not affected by the change in pH.

C. Compare the two results and the conditions that produced them. Based on this comparison describe a water treatment approach that could be used to remove Mg²⁺ from water.

Assumption: The temperature is 25C. Simplification: Neglect ionic strength.

Hint: Relationship between [H⁺] and [OH^-]: H₂O <--> H⁺ + OH^-; [H⁺][OH^-] = K_W = 10^-14 M² (25C)