4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)

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Stoichiometry

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NH3            Mass: g  or Gas Volume: L
O2             Mass: g  or Gas Volume: L
NO             Mass: g  or Gas Volume: L
H2O            Mass: g  or Gas Volume: L

Enthalpy of Reaction

[4ΔHf(NO (g)) + 6ΔHf(H2O (g))] - [4ΔHf(NH3 (g)) + 5ΔHf(O2 (g))]
[4(90.25) + 6(-241.82)] - [4(-46.11) + 5(0)] = -905.48 kJ
-905.48 kJ     (exothermic)

Entropy Change

[4ΔSf(NO (g)) + 6ΔSf(H2O (g))] - [4ΔSf(NH3 (g)) + 5ΔSf(O2 (g))]
[4(210.65) + 6(188.72)] - [4(192.34) + 5(205.03)] = 180.41 J/K
180.41 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[4ΔGf(NO (g)) + 6ΔGf(H2O (g))] - [4ΔGf(NH3 (g)) + 5ΔGf(O2 (g))]
[4(86.57) + 6(-228.59)] - [4(-16.48) + 5(0)] = -959.34 kJ
-959.34 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-959.27 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

1.1979768644933E+168
This process is favorable at 25°C.

Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; pp 135, 138, 194, 210, 219, 222, 224, 227.
Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; pp 131-2.
Kotz, John C., Treichel, Paul, and Weaver, Gabriela. Chemistry & Chemical Reactivity 6th ed.; Thomson Brooks/Cole: Belmont, CA, 2006; pp 147, 153.

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