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Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Acetylene decomposing to its elements
     2       +        
Acetylene
 
Reactants
 
Carbon
+
Hydrogen
 
Products
 
Products – Reactants
ΔfH
 
 
Σf-reactH
 
ΔfH
 
ΔfH
 
 
Σf-prodH
 
Σf-prodH - Σf-reactH = ΔrH
(226.7 x 1)
=
226.73
 
(0.0 x 2)
+
(0.0 x 1)
=
0.0
 
0.0 - 226.7 = -226.7 kJmol-1
                             
S
 
 
ΣreactS
 
S
 
S
 
 
ΣprodS
 
ΣprodS - ΣreactS = ΔrS
(0.201 x 1)
=
0.201
 
(0.006 x 2)
+
(0.131 x 1)
=
0.142
 
0.142 - 0.201 = -0.059 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
ΔrG   = ΔrH – (T298 x ΔrS)   =   -226.7– (298 x -0.059)  =
-209.2kJmol-1
ΔrH
=
-226.7 kJmol-1 Negative value: the reaction is exothermic
ΔrS
=
-0.059 kJK-1mol-1 Negative value: the system becomes less dispersed
ΔrG 298K
=
-209.2 kJmol-1 Negative value: the reaction is feasible (spontaneous)
Keq 298K
=
4.69 x 10+36 Value is greater than 1: the reaction proceeds to the right
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 3,857K (3,584°C)

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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –


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