Problem: Calculate the solubility of Mg(OH)2(s) in g/L in an aqueous solution buffered at pH = 8.60. The Ksp of Mg(OH)2 is 5.61 x 10-12.

FREE Expert Solution

STEP 1: Recall that ionic compounds such as Mg(OH)form ions when dissociating in water. 

Magnesium is in Group 2A so it’s charge is +2; The hydroxide ion, OHhas a charge of –1. 


Mg(OH)2(s)  Mg2+(aq) + 2OH(aq)

 **OH- has a subscript of 2 in Mg(OH)2 so it forms 2 OH- ions when it dissociates 


STEP 2: Make an ICE Chart

 



**We lose reactants (-x) and gain products (+x)


The equilibrium expression for the solubility product constant, Ksp is:


Ksp=productsreactants=Mg2+OH-2 

**Solids are ignored in Ksp expression

**Concentrations must be raised by the stoichiometric coefficient 

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Problem Details

Calculate the solubility of Mg(OH)2(s) in g/L in an aqueous solution buffered at pH = 8.60. The Ksp of Mg(OH)2 is 5.61 x 10-12.