ZnCl2 (s) → Zn+2 (aq) + 2 Cl-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Zn+2 (aq)) + 2ΔHf(Cl-1 (aq))] - [1ΔHf(ZnCl2 (s))]
[1(-153.9) + 2(-167.15)] - [1(-415.05)] = -73.15 kJ
-73.15 kJ     (exothermic)

Entropy Change

[1ΔSf(Zn+2 (aq)) + 2ΔSf(Cl-1 (aq))] - [1ΔSf(ZnCl2 (s))]
[1(-112.1) + 2(56.48)] - [1(108.37)] = -107.51 J/K
-107.51 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Zn+2 (aq)) + 2ΔGf(Cl-1 (aq))] - [1ΔGf(ZnCl2 (s))]
[1(-147.1) + 2(-131.25)] - [1(-369.43)] = -40.17 kJ
-40.17 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-41.10 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

10911164.7398248
This process is favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (10911164.7398248) will be used to calculate the equilibrium concentration for all species.

ZnCl2 Zn+2 Cl-1
Initial M   0 0
Change -x +x +2x
Equilibrium