4 Fe (s alpha) + 3 O2 (g) → 2 Fe2O3 (s hematite)

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Reaction Type:

Synthesis

Stoichiometry

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Fe             Mass: g
O2             Mass: g  or Gas Volume: L
Fe2O3          Mass: g
Heat Released: kJ

Enthalpy of Reaction

[2ΔHf(Fe2O3 (s hematite))] - [4ΔHf(Fe (s alpha)) + 3ΔHf(O2 (g))]
[2(-824.25)] - [4(0) + 3(0)] = -1648.5 kJ
-1,648.50 kJ     (exothermic)

Entropy Change

[2ΔSf(Fe2O3 (s hematite))] - [4ΔSf(Fe (s alpha)) + 3ΔSf(O2 (g))]
[2(87.4)] - [4(27.28) + 3(205.03)] = -549.41 J/K
-549.41 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[2ΔGf(Fe2O3 (s hematite))] - [4ΔGf(Fe (s alpha)) + 3ΔGf(O2 (g))]
[2(-742.24)] - [4(0) + 3(0)] = -1484.48 kJ
-1,484.48 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-1484.69 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

1.2137109021e+260
This process is favorable at 25°C.

Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 77.
Kotz, John C. and Treichel, Paul. Chemistry & Chemical Reactivity 4th ed.; Thomson Brooks/Cole: Belmont, CA, 1999; pp 149, 151.
Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 131.

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