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Enthalpy of Reaction
[2ΔHf(Br (g))] - [1ΔHf(Br2 (g))]
[2(111.88)] - [1(30.91)] = 192.85 kJ
192.85 kJ (endothermic)
[2ΔSf(Br (g))] - [1ΔSf(Br2 (g))]
[2(174.91)] - [1(245.35)] = 104.47 J/K
104.47 J/K (increase in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(Br (g))] - [1ΔGf(Br2 (g))]
[2(82.43)] - [1(3.14)] = 161.72 kJ
161.72 kJ (nonspontaneous)
From ΔG = ΔH - TΔS:
161.70 kJ (nonspontaneous)
Equilibrium Constant, K (at 298.15 K)
This process is not favorable at 25°C.
Atkins, Jones, and Laverman. Chemical Principles 6th ed.; W.H. Freeman and Company: New York, NY, 2013; p 428.