Ca3(PO4)2 (s beta) → 3 Ca+2 (aq) + 2 PO4-3 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[3ΔHf(Ca+2 (aq)) + 2ΔHf(PO4-3 (aq))] - [1ΔHf(Ca3(PO4)2 (s beta))]
[3(-542.83) + 2(-1277.38)] - [1(-4120.82)] = -62.4300000000003 kJ
-62.43 kJ     (exothermic)

Entropy Change

[3ΔSf(Ca+2 (aq)) + 2ΔSf(PO4-3 (aq))] - [1ΔSf(Ca3(PO4)2 (s beta))]
[3(-53.14) + 2(-221.75)] - [1(235.98)] = -838.9 J/K
-838.90 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[3ΔGf(Ca+2 (aq)) + 2ΔGf(PO4-3 (aq))] - [1ΔGf(Ca3(PO4)2 (s beta))]
[3(-553.54) + 2(-1018.8)] - [1(-3884.84)] = 186.62 kJ
186.62 kJ     (nonspontaneous)

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

Equilibrium Constant, K (at 298.15 K)

2.01266407461241E-33
This process is not favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (2.01266407461241E-33) will be used to calculate the equilibrium concentration for all species.

Ca3(PO4)2 Ca+2 PO4-3
Initial M   0 0
Change -x +3x +2x
Equilibrium