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List Thermochemical Reactions Build-a-Reaction Synthlet

Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Radical coupling of methane radicals to ethane
           +      
Methyl radical
+
Methyl radical
 
Reactants
 
Ethane
 
Products
 
Products – Reactants
Δf H ⦵
 
ΔfH⦵
 
Σf-react H ⦵
 
Δf H ⦵
 
 
 
Σf-prod H ⦵
 
Σf-prod H ⦵ - Σf-react H ⦵ = Δr H ⦵
(145.7 x 1)
+
(145.7 x 1)
=
291.38
 
(-84.7 x 1)
=
-84.7
 
-84.7 - 291.4 = -376.1 kJmol-1
                             
S ⦵
 
S⦵
 
Σreact S ⦵
 
S ⦵
 
 
 
Σprod S ⦵
 
Σprod S ⦵ - Σreact S ⦵ = Δr S ⦵
(0.194 x 1)
+
(0.194 x 1)
=
0.388
 
(0.230 x 1)
=
0.230
 
0.230 - 0.388 = -0.159 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
Δr G ⦵   = Δr H ⦵ – (T 298 x Δr S ⦵)   =   -376.1– (298 x-0.159)  =
-328.7kJmol-1
Δr H ⦵
=
 -376.1 kJmol-1 Negative value: the reaction is exothermic
Δr S ⦵
=
 -0.159 kJK-1mol-1 Negative value: the system becomes less dispersed
Δr G ⦵ 298K
=
 -328.7 kJmol-1 Negative value: the reaction is feasible (spontaneous)
K eq 298K
=
 4.18 x 10+57 Value is greater than 1: the reaction proceeds to the right
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 2,368K (2,095°C)
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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –

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