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Enthalpy of Reaction
[2ΔHf(F (g))] - [1ΔHf(F2 (g))]
[2(78.99)] - [1(0)] = 157.98 kJ
157.98 kJ (endothermic)
[2ΔSf(F (g))] - [1ΔSf(F2 (g))]
[2(158.66)] - [1(202.71)] = 114.61 J/K
114.61 J/K (increase in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(F (g))] - [1ΔGf(F2 (g))]
[2(61.92)] - [1(0)] = 123.84 kJ
123.84 kJ (nonspontaneous)
From ΔG = ΔH - TΔS:
123.81 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.