CaCl2 (s) → Ca+2 (aq) + 2 Cl-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Ca+2 (aq)) + 2ΔHf(Cl-1 (aq))] - [1ΔHf(CaCl2 (s))]
[1(-542.83) + 2(-167.15)] - [1(-795.8)] = -81.3300000000002 kJ
-81.33 kJ     (exothermic)

Entropy Change

[1ΔSf(Ca+2 (aq)) + 2ΔSf(Cl-1 (aq))] - [1ΔSf(CaCl2 (s))]
[1(-53.14) + 2(56.48)] - [1(104.6)] = -44.78 J/K
-44.78 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Ca+2 (aq)) + 2ΔGf(Cl-1 (aq))] - [1ΔGf(CaCl2 (s))]
[1(-553.54) + 2(-131.25)] - [1(-748.1)] = -67.9399999999999 kJ
-67.94 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-67.98 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

8.0026778597e+011
This process is favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (8.0026778597e+011) will be used to calculate the equilibrium concentration for all species.

CaCl2 Ca+2 Cl-1
Initial M   0 0
Change -x +x +2x
Equilibrium

Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 223.

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