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Enthalpy of Reaction
[2ΔHf(NH3 (g))] - [1ΔHf(N2 (g)) + 3ΔHf(H2 (g))]
[2(-46.11)] - [1(0) + 3(0)] = -92.22 kJ
-92.22 kJ (exothermic)
[2ΔSf(NH3 (g))] - [1ΔSf(N2 (g)) + 3ΔSf(H2 (g))]
[2(192.34)] - [1(191.5) + 3(130.59)] = -198.59 J/K
-198.59 J/K (decrease in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(NH3 (g))] - [1ΔGf(N2 (g)) + 3ΔGf(H2 (g))]
[2(-16.48)] - [1(0) + 3(0)] = -32.96 kJ
-32.96 kJ (spontaneous)
From ΔG = ΔH - TΔS:
-33.01 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; pp 115, 175, 223-4, 227.
Kotz, John C. and Treichel, Paul. Chemistry & Chemical Reactivity 4th ed.; Thomson Brooks/Cole: Belmont, CA, 1999; p 172.
Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 132.