Enter a mass or volume in one of the boxes below. Upon hitting submit, the stoichiometric equivalents will be calculated for the remaining reactants and products. All gases are assumed to be at STP.
Enthalpy of Reaction
[2ΔHf(NO2 (g))] - [1ΔHf(N2 (g)) + 2ΔHf(O2 (g))]
[2(33.18)] - [1(0) + 2(0)] = 66.36 kJ
66.36 kJ (endothermic)
[2ΔSf(NO2 (g))] - [1ΔSf(N2 (g)) + 2ΔSf(O2 (g))]
[2(239.95)] - [1(191.5) + 2(205.03)] = -121.66 J/K
-121.66 J/K (decrease in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(NO2 (g))] - [1ΔGf(N2 (g)) + 2ΔGf(O2 (g))]
[2(51.3)] - [1(0) + 2(0)] = 102.6 kJ
102.60 kJ (nonspontaneous)
From ΔG = ΔH - TΔS:
102.63 kJ (nonspontaneous)
Equilibrium Constant, K (at 298.15 K)
This process is not favorable at 25°C.
Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 222.