SiCl4 (g) + 1 O2 (g) + 2 H2 (g) → SiO2 (s quartz) + 4 HCl (g)

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Stoichiometry

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SiCl4          Mass: g  or Gas Volume: L
O2             Mass: g  or Gas Volume: L
H2             Mass: g  or Gas Volume: L
SiO2           Mass: g
HCl            Mass: g  or Gas Volume: L

Enthalpy of Reaction

[1ΔHf(SiO2 (s quartz)) + 4ΔHf(HCl (g))] - [1ΔHf(SiCl4 (g)) + 1ΔHf(O2 (g)) + 2ΔHf(H2 (g))]
[1(-910.94) + 4(-92.3)] - [1(-662.75) + 1(0) + 2(0)] = -617.39 kJ
-617.39 kJ     (exothermic)

Entropy Change

[1ΔSf(SiO2 (s quartz)) + 4ΔSf(HCl (g))] - [1ΔSf(SiCl4 (g)) + 1ΔSf(O2 (g)) + 2ΔSf(H2 (g))]
[1(41.84) + 4(186.77)] - [1(330.62) + 1(205.03) + 2(130.59)] = -7.90999999999985 J/K
-7.91 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(SiO2 (s quartz)) + 4ΔGf(HCl (g))] - [1ΔGf(SiCl4 (g)) + 1ΔGf(O2 (g)) + 2ΔGf(H2 (g))]
[1(-856.67) + 4(-95.31)] - [1(-622.58) + 1(0) + 2(0)] = -615.33 kJ
-615.33 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-615.03 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

6.41431684329117E+107
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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