CaSO4 (s) → Ca+2 (aq) + SO4-2 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Ca+2 (aq)) + 1ΔHf(SO4-2 (aq))] - [1ΔHf(CaSO4 (s))]
[1(-542.83) + 1(-909.27)] - [1(-1434.5)] = -17.5999999999999 kJ
-17.60 kJ     (exothermic)

Entropy Change

[1ΔSf(Ca+2 (aq)) + 1ΔSf(SO4-2 (aq))] - [1ΔSf(CaSO4 (s))]
[1(-53.14) + 1(20.08)] - [1(106.5)] = -139.56 J/K
-139.56 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Ca+2 (aq)) + 1ΔGf(SO4-2 (aq))] - [1ΔGf(CaSO4 (s))]
[1(-553.54) + 1(-744.63)] - [1(-1322)] = 23.8299999999999 kJ
23.83 kJ     (nonspontaneous)

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

Equilibrium Constant, K (at 298.15 K)

6.682397749e-005
This process is not favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (6.682397749e-005) will be used to calculate the equilibrium concentration for all species.

CaSO4 Ca+2 SO4-2
Initial M   0 0
Change -x +x +x
Equilibrium