## 2 KNO3 (aq) → 2 KNO2 (aq) + O2 (g)

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Decomposition

## Stoichiometry

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 Heat Added: kJ KNO3           Mass: g or Solution Volume: mL of Concentration: mol/L KNO2           Mass: g O2             Mass: g or Gas Volume: L

## 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)

## Entropy Change

[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)

1.0840232887e-026
This process is not favorable at 25°C.

## Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 77.