4 Al (s) + 3 O2 (g) + 6 H2O (ℓ) → 4 Al(OH)3 (s)

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Reaction Type:

Synthesis

Stoichiometry

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Al             Mass: g
O2             Mass: g  or Gas Volume: L
H2O            Mass: g
Al(OH)3        Mass: g

Enthalpy of Reaction

[4ΔHf(Al(OH)3 (s))] - [4ΔHf(Al (s)) + 3ΔHf(O2 (g)) + 6ΔHf(H2O (ℓ))]
[4(-1284.49)] - [4(0) + 3(0) + 6(-285.83)] = -3422.98 kJ
-3,422.98 kJ     (exothermic)

Entropy Change

[4ΔSf(Al(OH)3 (s))] - [4ΔSf(Al (s)) + 3ΔSf(O2 (g)) + 6ΔSf(H2O (ℓ))]
[4(71.13)] - [4(28.33) + 3(205.03) + 6(69.91)] = -863.35 J/K
-863.35 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[4ΔGf(Al(OH)3 (s))] - [4ΔGf(Al (s)) + 3ΔGf(O2 (g)) + 6ΔGf(H2O (ℓ))]
[4(-1305.83)] - [4(0) + 3(0) + 6(-237.18)] = -3800.24 kJ
-3,800.24 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-3165.57 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)


Reference(s):

Halka, Monica and Nordstrom, Brian. Metals & Metalloids; Infobase Publishing: New York, NY, 2011; p 8.

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