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Enthalpy of Reaction
[2ΔHf(KNO2 (aq)) + 1ΔHf(O2 (g))] - [2ΔHf(KNO3 (aq))]
[2(-357) + 1(0)] - [2(-459.76)] = 205.52 kJ
205.52 kJ (endothermic)
[2ΔSf(KNO2 (aq)) + 1ΔSf(O2 (g))] - [2ΔSf(KNO3 (aq))]
[2(242.66) + 1(205.03)] - [2(248.94)] = 192.47 J/K
192.47 J/K (increase in entropy)
Free Energy of Reaction (at 298.15 K)
From ΔGf° values:
[2ΔGf(KNO2 (aq)) + 1ΔGf(O2 (g))] - [2ΔGf(KNO3 (aq))]
[2(-320.54) + 1(0)] - [2(-394.64)] = 148.2 kJ
148.20 kJ (nonspontaneous)
From ΔG = ΔH - TΔS:
148.14 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 77.