SiCl4 (g) + 1 O2 (g) → SiO2 (s quartz) + 2 Cl2 (g)

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Stoichiometry

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SiCl4          Mass: g  or Gas Volume: L
O2             Mass: g  or Gas Volume: L
SiO2           Mass: g
Cl2            Mass: g  or Gas Volume: L
Heat Released: kJ

Enthalpy of Reaction

[1ΔHf(SiO2 (s quartz)) + 2ΔHf(Cl2 (g))] - [1ΔHf(SiCl4 (g)) + 1ΔHf(O2 (g))]
[1(-910.94) + 2(0)] - [1(-662.75) + 1(0)] = -248.19 kJ
-248.19 kJ     (exothermic)

Entropy Change

[1ΔSf(SiO2 (s quartz)) + 2ΔSf(Cl2 (g))] - [1ΔSf(SiCl4 (g)) + 1ΔSf(O2 (g))]
[1(41.84) + 2(222.97)] - [1(330.62) + 1(205.03)] = -47.87 J/K
-47.87 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(SiO2 (s quartz)) + 2ΔGf(Cl2 (g))] - [1ΔGf(SiCl4 (g)) + 1ΔGf(O2 (g))]
[1(-856.67) + 2(0)] - [1(-622.58) + 1(0)] = -234.09 kJ
-234.09 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-233.92 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

1.0305656175e+041
This process is favorable at 25°C.

Reference(s):

Swaddle, T.W. Inorganic Chemistry; Academic Press: San Diego, 1997; p 143.

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