NH4I (s) → NH4+1 (aq) + I-1 (aq)

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Reaction Type:

Dissociation of an ionic compound in water

Enthalpy of Reaction

[1ΔHf(NH4+1 (aq)) + 1ΔHf(I-1 (aq))] - [1ΔHf(NH4I (s))]
[1(-132.51) + 1(-55.19)] - [1(-201.42)] = 13.72 kJ
13.72 kJ     (endothermic)

Entropy Change

[1ΔSf(NH4+1 (aq)) + 1ΔSf(I-1 (aq))] - [1ΔSf(NH4I (s))]
[1(113.39) + 1(111.29)] - [1(117.15)] = 107.53 J/K
107.53 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(NH4+1 (aq)) + 1ΔGf(I-1 (aq))] - [1ΔGf(NH4I (s))]
[1(-79.37) + 1(-51.59)] - [1(-112.55)] = -18.41 kJ
-18.41 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-18.34 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

1680.62927409685
This process is favorable at 25°C.

Enter an initial concentration for the ionic compound. Upon hitting submit, Ksp (1680.62927409685) will be used to calculate the equilibrium concentration for all species.

NH4I NH4+1 I-1
Initial M   0 0
Change -x +x +x
Equilibrium