STEP 1: Recall that ionic compounds such as Mg(OH)2 form ions when dissociating in water.
Magnesium is in Group 2A so it’s charge is +2; The hydroxide ion, OH–, has 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:
**Solids are ignored in Ksp expression
**Concentrations must be raised by the stoichiometric coefficient
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.