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List Thermochemical Reactions Build-a-Reaction Synthlet

Thermochemistry: Play With Reaction Synthlet


    
   or    Kelvin        
Oxidation of ammonia to nitric oxide with hydrogen peroxide
    2       +       5 2       +         8
Ammonia, aqueous
+
Hydrogen peroxide
 
Reactants
 
Nitric oxide
+
Water
 
Products
 
Products – Reactants
Δf H ⦵
 
ΔfH⦵
 
Σf-react H ⦵
 
Δf H ⦵
 
ΔfH
 
 
Σf-prod H ⦵
 
Σf-prod H ⦵ - Σf-react H ⦵ = Δr H ⦵
(-80.3 x 2)
+
(-187.8 x 5)
=
-1,099.48
 
(90.3 x 2)
+
(-285.8 x 8)
=
-2,106.1
 
-2,106.1 - -1,099.5 = -1,006.7 kJmol-1
                             
S ⦵
 
S⦵
 
Σreact S ⦵
 
S ⦵
 
S
 
 
Σprod S ⦵
 
Σprod S ⦵ - Σreact S ⦵ = Δr S ⦵
(0.111 x 2)
+
(0.110 x 5)
=
0.771
 
(0.211 x 2)
+
(0.070 x 8)
=
0.981
 
0.981 - 0.771 = 0.210 kJK-1mol-1
Gibbs free energy at 298K (standard conditions and standard temperature):
 
Δr G ⦵   = Δr H ⦵ – (T 298 x Δr S ⦵)   =   -1,006.7– (298 x0.210)  =
-1,069.3kJmol-1
Δr H ⦵
=
 -1,006.7 kJmol-1 Negative value: the reaction is exothermic
Δr S ⦵
=
 +0.210 kJK-1mol-1 Positive value: the system becomes more dispersed
Δr G ⦵ 298K
=
 -1,069.3 kJmol-1 Negative value: the reaction is feasible (spontaneous)
K eq 298K
=
 >10100 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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© Mark R. Leach 1999 –

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