ZnI2 (s) → Zn+2 (aq) + 2 I-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Zn+2 (aq)) + 2ΔHf(I-1 (aq))] - [1ΔHf(ZnI2 (s))]
[1(-153.9) + 2(-55.19)] - [1(-208.03)] = -56.25 kJ
-56.25 kJ     (exothermic)

Entropy Change

[1ΔSf(Zn+2 (aq)) + 2ΔSf(I-1 (aq))] - [1ΔSf(ZnI2 (s))]
[1(-112.1) + 2(111.29)] - [1(161.08)] = -50.6 J/K
-50.60 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Zn+2 (aq)) + 2ΔGf(I-1 (aq))] - [1ΔGf(ZnI2 (s))]
[1(-147.1) + 2(-51.59)] - [1(-208.95)] = -41.33 kJ
-41.33 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-41.16 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

17422305.648
This process is favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (17422305.648) will be used to calculate the equilibrium concentration for all species.

ZnI2 Zn+2 I-1
Initial M   0 0
Change -x +x +2x
Equilibrium