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Enthalpy of Reaction
[2ΔHf(NaCl (s))] - [2ΔHf(Na (s)) + 1ΔHf(Cl2 (g))]
[2(-410.99)] - [2(0) + 1(0)] = -821.98 kJ
-821.98 kJ (exothermic)
[2ΔSf(NaCl (s))] - [2ΔSf(Na (s)) + 1ΔSf(Cl2 (g))]
[2(72.38)] - [2(51.46) + 1(222.97)] = -181.13 J/K
-181.13 J/K (decrease in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(NaCl (s))] - [2ΔGf(Na (s)) + 1ΔGf(Cl2 (g))]
[2(-384.05)] - [2(0) + 1(0)] = -768.1 kJ
-768.10 kJ (spontaneous)
From ΔG = ΔH - TΔS:
-767.98 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 71.
Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 134.