MgCl2 (s) → Mg+2 (aq) + 2 Cl-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(Mg+2 (aq)) + 2ΔHf(Cl-1 (aq))] - [1ΔHf(MgCl2 (s))]
[1(-466.85) + 2(-167.15)] - [1(-641.62)] = -159.53 kJ
-159.53 kJ     (exothermic)

Entropy Change

[1ΔSf(Mg+2 (aq)) + 2ΔSf(Cl-1 (aq))] - [1ΔSf(MgCl2 (s))]
[1(-138.07) + 2(56.48)] - [1(89.62)] = -114.73 J/K
-114.73 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Mg+2 (aq)) + 2ΔGf(Cl-1 (aq))] - [1ΔGf(MgCl2 (s))]
[1(-454.8) + 2(-131.25)] - [1(-592.12)] = -125.18 kJ
-125.18 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-125.32 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

8.5468772399e+021
This process is favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (8.5468772399e+021) will be used to calculate the equilibrium concentration for all species.

MgCl2 Mg+2 Cl-1
Initial M   0 0
Change -x +x +2x
Equilibrium