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Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Decomposition of ozone to oxygen
    2 3
Ozone
 
Reactants
 
Oxygen
 
Products
 
Products – Reactants
ΔfH
 
 
Σf-reactH
 
ΔfH
 
 
 
Σf-prodH
 
Σf-prodH - Σf-reactH = ΔrH
(142.7 x 2)
=
285.40
 
(0.0 x 3)
=
0.0
 
0.0 - 285.4 = -285.4 kJmol-1
                             
S
 
 
ΣreactS
 
S
 
 
 
ΣprodS
 
ΣprodS - ΣreactS = ΔrS
(0.239 x 2)
=
0.478
 
(0.205 x 3)
=
0.615
 
0.615 - 0.478 = 0.138 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
ΔrG   = ΔrH – (T298 x ΔrS)   =   -285.4– (298 x 0.138)  =
-326.4kJmol-1
ΔrH
=
-285.4 kJmol-1 Negative value: the reaction is exothermic
ΔrS
=
+0.138 kJK-1mol-1 Positive value: the system becomes more dispersed
ΔrG 298K
=
-326.4 kJmol-1 Negative value: the reaction is feasible (spontaneous)
Keq 298K
=
1.62 x 10+57 Value is greater than 1: the reaction proceeds to the right
No equilibrium temperature: this reaction is feasible at all temperatures

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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –


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