Mg(OH)2 (s) → Mg+2 (aq) + 2 OH-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Mg+2 (aq)) + 2ΔHf(OH-1 (aq))] - [1ΔHf(Mg(OH)2 (s))]
[1(-466.85) + 2(-229.99)] - [1(-924.66)] = -2.17000000000007 kJ
-2.17 kJ     (exothermic)

Entropy Change

[1ΔSf(Mg+2 (aq)) + 2ΔSf(OH-1 (aq))] - [1ΔSf(Mg(OH)2 (s))]
[1(-138.07) + 2(-10.75)] - [1(63.18)] = -222.75 J/K
-222.75 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Mg+2 (aq)) + 2ΔGf(OH-1 (aq))] - [1ΔGf(Mg(OH)2 (s))]
[1(-454.8) + 2(-157.28)] - [1(-833.87)] = 64.51 kJ
64.51 kJ     (nonspontaneous)

From ΔG = ΔH - TΔS:
64.24 kJ     (nonspontaneous)

Equilibrium Constant, K (at 298.15 K)

4.98549291255928E-12
This process is not favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (4.98549291255928E-12) will be used to calculate the equilibrium concentration for all species.

Mg(OH)2 Mg+2 OH-1
Initial M   0 0
Change -x +x +2x
Equilibrium