## Sb2S3 (s black) + 1 Fe (s alpha) → Sb (s) + FeS (s pyrrhotite)

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## Stoichiometry

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 Heat Added: kJ Sb2S3          Mass: g Fe             Mass: g Sb             Mass: g FeS            Mass: g

## Enthalpy of Reaction

[1ΔHf(Sb (s)) + 1ΔHf(FeS (s pyrrhotite))] - [1ΔHf(Sb2S3 (s black)) + 1ΔHf(Fe (s alpha))]
[1(0) + 1(-100)] - [1(-174.89) + 1(0)] = 74.89 kJ
74.89 kJ     (endothermic)

## Entropy Change

[1ΔSf(Sb (s)) + 1ΔSf(FeS (s pyrrhotite))] - [1ΔSf(Sb2S3 (s black)) + 1ΔSf(Fe (s alpha))]
[1(45.69) + 1(60.29)] - [1(182) + 1(27.28)] = -103.3 J/K
-103.30 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Sb (s)) + 1ΔGf(FeS (s pyrrhotite))] - [1ΔGf(Sb2S3 (s black)) + 1ΔGf(Fe (s alpha))]
[1(0) + 1(-100.42)] - [1(-173.64) + 1(0)] = 73.22 kJ
73.22 kJ     (nonspontaneous)

From ΔG = ΔH - TΔS:
105.69 kJ     (nonspontaneous)

## Equilibrium Constant, K (at 298.15 K)

1.4849000252e-013
This process is not favorable at 25°C.

## Reference(s):

Atkins, Jones, and Laverman. Chemical Principles 6th ed.; W.H. Freeman and Company: New York, NY, 2013; p F94.