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List Thermochemical Reactions Build-a-Reaction Synthlet

Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Haber ammonia synthesis
           +       3 2
Nitrogen
+
Hydrogen
 
Reactants
 
Ammonia
 
Products
 
Products – Reactants
Δf H ⦵
 
ΔfH⦵
 
Σf-react H ⦵
 
Δf H ⦵
 
 
 
Σf-prod H ⦵
 
Σf-prod H ⦵ - Σf-react H ⦵ = Δr H ⦵
(0.0 x 1)
+
(0.0 x 3)
=
0.00
 
(-46.1 x 2)
=
-92.2
 
-92.2 - 0.0 = -92.2 kJmol-1
                             
S ⦵
 
S⦵
 
Σreact S ⦵
 
S ⦵
 
 
 
Σprod S ⦵
 
Σprod S ⦵ - Σreact S ⦵ = Δr S ⦵
(0.192 x 1)
+
(0.131 x 3)
=
0.584
 
(0.192 x 2)
=
0.385
 
0.385 - 0.584 = -0.199 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
Δr G ⦵   = Δr H ⦵ – (T 298 x Δr S ⦵)   =   -92.2– (298 x-0.199)  =
-33.0kJmol-1
Δr H ⦵
=
 -92.2 kJmol-1 Negative value: the reaction is exothermic
Δr S ⦵
=
 -0.199 kJK-1mol-1 Negative value: the system becomes less dispersed
Δr G ⦵ 298K
=
 -33.0 kJmol-1 Negative value: the reaction is feasible (spontaneous)
K eq 298K
=
 6.07 x 105 Value is greater than 1: the reaction proceeds to the right
ΔG° = 0.0, and the system is at equilibrium, at a temperature of 464K (191°C)
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List Thermochemical Reactions Build-a-Reaction Synthlet

© Mark R. Leach 1999 –

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