## 2 H2 (g) + 1 O2 (g) → 2 H2O (ℓ)

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Synthesis

## Stoichiometry

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 H2             Mass: g or Gas Volume: L O2             Mass: g or Gas Volume: L H2O            Mass: g Heat Released: kJ

## Enthalpy of Reaction

[2ΔHf(H2O (ℓ))] - [2ΔHf(H2 (g)) + 1ΔHf(O2 (g))]
[2(-285.83)] - [2(0) + 1(0)] = -571.66 kJ
-571.66 kJ     (exothermic)

## Entropy Change

[2ΔSf(H2O (ℓ))] - [2ΔSf(H2 (g)) + 1ΔSf(O2 (g))]
[2(69.91)] - [2(130.59) + 1(205.03)] = -326.39 J/K
-326.39 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[2ΔGf(H2O (ℓ))] - [2ΔGf(H2 (g)) + 1ΔGf(O2 (g))]
[2(-237.18)] - [2(0) + 1(0)] = -474.36 kJ
-474.36 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-474.35 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

1.2849928175e+083
This process is favorable at 25°C.

## Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; pp 223-4.