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Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Hydrogenation of 1-butene
           +      
1-Butene
+
Hydrogen
 
Reactants
 
Butane
 
Products
 
Products – Reactants
ΔfH
 
ΔfH
 
Σf-reactH
 
ΔfH
 
 
 
Σf-prodH
 
Σf-prodH - Σf-reactH = ΔrH
(-0.1 x 1)
+
(0.0 x 1)
=
-0.13
 
(-126.2 x 1)
=
-126.2
 
-126.2 - -0.1 = -126.0 kJmol-1
                             
S
 
S
 
ΣreactS
 
S
 
 
 
ΣprodS
 
ΣprodS - ΣreactS = ΔrS
(0.306 x 1)
+
(0.131 x 1)
=
0.436
 
(0.310 x 1)
=
0.310
 
0.310 - 0.436 = -0.126 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
ΔrG   = ΔrH – (T298 x ΔrS)   =   -126.0– (298 x -0.126)  =
-88.4kJmol-1
ΔrH
=
-126.0 kJmol-1 Negative value: the reaction is exothermic
ΔrS
=
-0.126 kJK-1mol-1 Negative value: the system becomes less dispersed
ΔrG 298K
=
-88.4 kJmol-1 Negative value: the reaction is feasible (spontaneous)
Keq 298K
=
3.15 x 10+15 Value is greater than 1: the reaction proceeds to the right
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 999K (726°C)

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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –


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