H2SO3 (aq) → SO2 (g) + H2O (ℓ)

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Reaction Type:

Decomposition

Stoichiometry

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H2SO3          Mass: g  or Solution Volume: mL of Concentration: mol/L
SO2            Mass: g  or Gas Volume: L
H2O            Mass: g

Enthalpy of Reaction

[1ΔHf(SO2 (g)) + 1ΔHf(H2O (ℓ))] - [1ΔHf(H2SO3 (aq))]
[1(-296.83) + 1(-285.83)] - [1(-635.55)] = 52.89 kJ
52.89 kJ     (endothermic)

Entropy Change

[1ΔSf(SO2 (g)) + 1ΔSf(H2O (ℓ))] - [1ΔSf(H2SO3 (aq))]
[1(248.11) + 1(69.91)] - [1(-29.29)] = 347.31 J/K
347.31 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(SO2 (g)) + 1ΔGf(H2O (ℓ))] - [1ΔGf(H2SO3 (aq))]
[1(-300.19) + 1(-237.18)] - [1(-486.6)] = -50.77 kJ
-50.77 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-50.66 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

785261129.113537
This process is favorable at 25°C.