Ca(OH)2 (s) → Ca+2 (aq) + 2 OH-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Ca+2 (aq)) + 2ΔHf(OH-1 (aq))] - [1ΔHf(Ca(OH)2 (s))]
[1(-542.83) + 2(-229.99)] - [1(-986.17)] = -16.6400000000001 kJ
-16.64 kJ     (exothermic)

Entropy Change

[1ΔSf(Ca+2 (aq)) + 2ΔSf(OH-1 (aq))] - [1ΔSf(Ca(OH)2 (s))]
[1(-53.14) + 2(-10.75)] - [1(83.39)] = -158.03 J/K
-158.03 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Ca+2 (aq)) + 2ΔGf(OH-1 (aq))] - [1ΔGf(Ca(OH)2 (s))]
[1(-553.54) + 2(-157.28)] - [1(-898.51)] = 30.4100000000001 kJ
30.41 kJ     (nonspontaneous)

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

Equilibrium Constant, K (at 298.15 K)

4.70004539632578E-06
This process is not favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (4.70004539632578E-06) will be used to calculate the equilibrium concentration for all species.

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