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Enthalpy of Reaction
[1ΔHf(KBr (s))] - [1ΔHf(K (g)) + 1ΔHf(Br (g))]
[1(-392.17)] - [1(89.12) + 1(111.88)] = -593.17 kJ
-593.17 kJ (exothermic)
[1ΔSf(KBr (s))] - [1ΔSf(K (g)) + 1ΔSf(Br (g))]
[1(96.44)] - [1(90.04) + 1(174.91)] = -168.51 J/K
-168.51 J/K (decrease in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[1ΔGf(KBr (s))] - [1ΔGf(K (g)) + 1ΔGf(Br (g))]
[1(-379.2)] - [1(60.67) + 1(82.43)] = -522.3 kJ
-522.30 kJ (spontaneous)
From ΔG = ΔH - TΔS:
-542.93 kJ (spontaneous)
Equilibrium Constant, K (at 298.15 K)
This process is favorable at 25°C.
Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 305.