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The Ksp of magnesium hydroxide, Mg(OH)2, is 1.2 x 10-11, so setting 4s3 = Ksp, results in s = 1.4 x 10-4. This leads to an [OH-] = 2.8 x 10-4 (i.e., a pOH=3.55), thus a pH of 10.45. Given the aforementioned information and resulting calculations, comment on the solubility of Mg(OH)2 at pH values: 1) less than 10.45 and, 2) greater than 10.45

Answer :

Answer:

1) less than 10.45 : Increase the solubility

2) greater than 10.45: decrease the solubility

Explanation:

The dissolution equation for magnesium hydroxide is:

[tex]Mg(OH)_{2}--->Mg^{+2}+2OH^{-}[/tex]

Thus there is formation of hydroxide ion during dissollution of magnesium hydroxide.

If the pH value increases from 10.45 to higher value, it means we are decreasing the concentration of [H⁺] or increasing the concentration of [OH⁻]

Increasing the concentration of [OH⁻] will shift the equilibrium towards reactant side. Thus it will decrease the solubility of magnesium hydroxide.

If the pH value decreases from 10.45 to lower value, it means we are increasing the concentration of [H⁺] or decreasing the concentration of [OH⁻]

decreasing the concentration of [OH⁻] will shift the equilibrium towards product side. Thus it will increase the solubility of magnesium hydroxide.

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