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Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Carbon plus water shift reaction
           +             +        
Carbon
+
Steam
 
Reactants
 
Carbon monoxide
+
Hydrogen
 
Products
 
Products – Reactants
ΔfH
 
ΔfH
 
Σf-reactH
 
ΔfH
 
ΔfH
 
 
Σf-prodH
 
Σf-prodH - Σf-reactH = ΔrH
(0.0 x 1)
+
(-241.8 x 1)
=
-241.82
 
(-110.5 x 1)
+
(0.0 x 1)
=
-110.5
 
-110.5 - -241.8 = 131.3 kJmol-1
                             
S
 
S
 
ΣreactS
 
S
 
S
 
 
ΣprodS
 
ΣprodS - ΣreactS = ΔrS
(0.006 x 1)
+
(0.189 x 1)
=
0.195
 
(0.198 x 1)
+
(0.131 x 1)
=
0.328
 
0.328 - 0.195 = 0.134 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
ΔrG   = ΔrH – (T298 x ΔrS)   =   131.3– (298 x 0.134)  =
+91.4kJmol-1
ΔrH
=
+131.3 kJmol-1 Positive value: the reaction is endothermic
ΔrS
=
+0.134 kJK-1mol-1 Positive value: the system becomes more dispersed
ΔrG 298K
=
+91.4 kJmol-1 Positive value: the reaction is not feasible (spontaneous)
Keq 298K
=
9.45 x 10-17 Value is less than 1: the reaction proceeds to the left
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 981K (708°C)

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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –


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