Ca(OH)2 (aq) + 2 NH4Br (s) → CaBr2 (aq) + 2 H2O (ℓ) + 2 NH3 (g)

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Reaction Type:

Double Displacement/Decomposition of Ammonium Hydroxide

Stoichiometry

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Heat Added: kJ
Ca(OH)2        Mass: g  or Solution Volume: mL of Concentration: mol/L
NH4Br          Mass: g
CaBr2          Mass: g
H2O            Mass: g
NH3            Mass: g  or Gas Volume: L

Enthalpy of Reaction

[1ΔHf(CaBr2 (aq)) + 2ΔHf(H2O (ℓ)) + 2ΔHf(NH3 (g))] - [1ΔHf(Ca(OH)2 (aq)) + 2ΔHf(NH4Br (s))]
[1(-785.93) + 2(-285.83) + 2(-46.11)] - [1(-1002.81) + 2(-270.83)] = 94.6599999999999 kJ
94.66 kJ     (endothermic)

Entropy Change

[1ΔSf(CaBr2 (aq)) + 2ΔSf(H2O (ℓ)) + 2ΔSf(NH3 (g))] - [1ΔSf(Ca(OH)2 (aq)) + 2ΔSf(NH4Br (s))]
[1(111.7) + 2(69.91) + 2(192.34)] - [1(-74.64) + 2(112.97)] = 484.9 J/K
484.90 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(CaBr2 (aq)) + 2ΔGf(H2O (ℓ)) + 2ΔGf(NH3 (g))] - [1ΔGf(Ca(OH)2 (aq)) + 2ΔGf(NH4Br (s))]
[1(-761.48) + 2(-237.18) + 2(-16.48)] - [1(-868.1) + 2(-175.31)] = -50.0800000000004 kJ
-50.08 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-49.91 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

594462691.97
This process is favorable at 25°C.