## SO2 (g) + 2 NaOH (s) → Na2SO3 (s) + H2O (ℓ)

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## Stoichiometry

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 SO2            Mass: g or Gas Volume: L NaOH           Mass: g Na2SO3         Mass: g H2O            Mass: g Heat Released: kJ

## Enthalpy of Reaction

[1ΔHf(Na2SO3 (s)) + 1ΔHf(H2O (ℓ))] - [1ΔHf(SO2 (g)) + 2ΔHf(NaOH (s))]
[1(-1090.35) + 1(-285.83)] - [1(-296.83) + 2(-426.73)] = -225.89 kJ
-225.89 kJ     (exothermic)

## Entropy Change

[1ΔSf(Na2SO3 (s)) + 1ΔSf(H2O (ℓ))] - [1ΔSf(SO2 (g)) + 2ΔSf(NaOH (s))]
[1(146.02) + 1(69.91)] - [1(248.11) + 2(64.43)] = -161.04 J/K
-161.04 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Na2SO3 (s)) + 1ΔGf(H2O (ℓ))] - [1ΔGf(SO2 (g)) + 2ΔGf(NaOH (s))]
[1(-1002.07) + 1(-237.18)] - [1(-300.19) + 2(-379.07)] = -180.92 kJ
-180.92 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-177.88 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

4.9839806128e+031
This process is favorable at 25°C.

## Reference(s):

Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 135.