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List Thermochemical Reactions Build-a-Reaction Synthlet

Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Partial oxidation of methane to acetylene, H2 and CO
    6       +       2       +         2       +         10
Methane
+
Oxygen
 
Reactants
 
Acetylene
+
Carbon monoxide
+
Hydrogen
 
Products
 
Products – Reactants
Δf H ⦵
 
ΔfH⦵
 
Σf-react H ⦵
 
Δf H ⦵
 
ΔfH
 
ΔfH
 
Σf-prod H ⦵
 
Σf-prod H ⦵ - Σf-react H ⦵ = Δr H ⦵
(-74.8 x 6)
+
(0.0 x 1)
=
-448.86
 
(226.7 x 2)
+
(-110.5 x 2)
+
(-110.5 x 2)
=
232.4
 
232.4 - -448.9 = 681.3 kJmol-1
                             
S ⦵
 
S⦵
 
Σreact S ⦵
 
S ⦵
 
S
 
S
 
Σprod S ⦵
 
Σprod S ⦵ - Σreact S ⦵ = Δr S ⦵
(0.186 x 6)
+
(0.205 x 1)
=
1.323
 
(0.201 x 2)
+
(0.198 x 2)
+
(0.198 x 2)
=
2.104
 
2.104 - 1.323 = 0.781 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
Δr G ⦵   = Δr H ⦵ – (T 298 x Δr S ⦵)   =   681.3– (298 x0.781)  =
+448.4kJmol-1
Δr H ⦵
=
 +681.3 kJmol-1 Positive value: the reaction is endothermic
Δr S ⦵
=
 +0.781 kJK-1mol-1 Positive value: the system becomes more dispersed
Δr G ⦵ 298K
=
 +448.4 kJmol-1 Positive value: the reaction is not feasible (spontaneous)
K eq 298K
=
 2.51 x 10-79 Value is less than 1: the reaction proceeds to the left
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 872K (599°C)
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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –

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