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Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Carbon monoxide + hydrogen gives methane + water equilibrium
           +       3       +        
Carbon monoxide
+
Hydrogen
 
Reactants
 
Methane
+
Water
 
Products
 
Products – Reactants
ΔfH
 
ΔfH
 
Σf-reactH
 
ΔfH
 
ΔfH
 
 
Σf-prodH
 
Σf-prodH - Σf-reactH = ΔrH
(-110.5 x 1)
+
(0.0 x 3)
=
-110.53
 
(-74.8 x 1)
+
(-285.8 x 1)
=
-360.6
 
-360.6 - -110.5 = -250.1 kJmol-1
                             
S
 
S
 
ΣreactS
 
S
 
S
 
 
ΣprodS
 
ΣprodS - ΣreactS = ΔrS
(0.198 x 1)
+
(0.131 x 3)
=
0.590
 
(0.186 x 1)
+
(0.070 x 1)
=
0.256
 
0.256 - 0.590 = -0.334 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
ΔrG   = ΔrH – (T298 x ΔrS)   =   -250.1– (298 x -0.334)  =
-150.7kJmol-1
ΔrH
=
-250.1 kJmol-1 Negative value: the reaction is exothermic
ΔrS
=
-0.334 kJK-1mol-1 Negative value: the system becomes less dispersed
ΔrG 298K
=
-150.7 kJmol-1 Negative value: the reaction is feasible (spontaneous)
Keq 298K
=
2.61 x 10+26 Value is greater than 1: the reaction proceeds to the right
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 750K (477°C)

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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –


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