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Table 15 Standard free energy of formation (Kcal/mole)
|
Compound |
DG0f |
Compound |
DG0f |
|
H2O (g) |
-54.64 |
CO (g) |
-32.81 |
|
H2O (l) |
-56.69 |
CO2 (g) |
-94.26 |
|
HF (g) |
-64.7 |
NO (g) |
+20.72 |
|
HCl (g) |
-22.77 |
NO2 (g) |
+12.39 |
|
HBr (g) |
-12.77 |
CaO(s) |
-144.4 |
|
HI (g) |
+0.31 |
Ca(OH) 2 (s) |
-214.33 |
|
NH3 (g) |
-3.98 |
O2 (g) |
0 |
|
SO2 (g) |
-71.79 |
S (s) |
0 |
Based on the above standard free energies, the free energy change of a chemical reaction may be calculated.
Example : 2NO (g) + O2 (g) NO2 (g)
DG reaction = DG products - DG reactants
= + 12.39 - ( 20.72 + 0 )
= - 8.33 K Cal
which indicates that the reaction occurs spontaneously.
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