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Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
The Contact process
    2       +       2
Sulfur dioxide
+
Oxygen
 
Reactants
 
Sulfur trioxide
 
Products
 
Products – Reactants
ΔfH
 
ΔfH
 
Σf-reactH
 
ΔfH
 
 
 
Σf-prodH
 
Σf-prodH - Σf-reactH = ΔrH
(-296.8 x 2)
+
(0.0 x 1)
=
-593.66
 
(-395.7 x 2)
=
-791.4
 
-791.4 - -593.7 = -197.8 kJmol-1
                             
S
 
S
 
ΣreactS
 
S
 
 
 
ΣprodS
 
ΣprodS - ΣreactS = ΔrS
(0.248 x 2)
+
(0.205 x 1)
=
0.702
 
(0.257 x 2)
=
0.514
 
0.514 - 0.702 = -0.188 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
ΔrG   = ΔrH – (T298 x ΔrS)   =   -197.8– (298 x -0.188)  =
-141.7kJmol-1
ΔrH
=
-197.8 kJmol-1 Negative value: the reaction is exothermic
ΔrS
=
-0.188 kJK-1mol-1 Negative value: the system becomes less dispersed
ΔrG 298K
=
-141.7 kJmol-1 Negative value: the reaction is feasible (spontaneous)
Keq 298K
=
6.98 x 10+24 Value is greater than 1: the reaction proceeds to the right
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 1,052K (779°C)

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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –


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