Untitled - Aerobib - Universidad Politécnica de Madrid

8 CHAPTER 1. THERMOCHEMISTRY
Inorganic Substances
Substance State h 0 s 0 ∆G 0
H 2 gas 0.00 5.482 0
H gas 51 675.60 27.176 48 575
Br 2 liquid 0.00 0.228 0
Br gas 3 342.25 0.543 19 690
HBr gas -107.01 0.586 -12 720
O 2 gas 0.00 1.531 0
O gas 3 697.44 2.404 54 994
O 3 gas 708.33 1.183 39 060
H 2O gas -3 208.15 2.504 -54 635
H 2 O liquid -3 792.02 0.928 -56 690
N 2 gas 0.00 1.634 0
N gas 6108.37 2.614 81 476
NH 3 gas -648.19 2.701 -3 976
NO gas 719.81 1.678 20 719
NO 2 gas 175.86 1.249 12 390
N 2 O 4 gas 25.09 0.790 23 491
N 2O gas 442.79 1.195 24 760
HNO 3 liquid -657.04 0.591 -19 100
C(graphite) solid 0.113 0
C(diamond) solid 37.72 0.049 685
CO gas -943.09 1.689 -32 808
CO 2 gas -2 137.06 1.16 -94 259
Table 1.2: Formation enthalpies (cal/gr),
(cal/mol). Inorganic substances.
entropies (cal gr −1 K −1 ) and free energies
where s 0 is the entropy of the gas at pressure p 0 and at temperature T 0 . The third law of
Thermodynamics assigns zero values to the entropies of all substances at the absolute
zero of temperature. This determines the values of s 0 without the need of a convention
as for the enthalpy case. 5
various substances.
Tables 1.2-1.4 also include the formation entropies of the
Let s 0 be the entropy of the gas at temperature T and standard pressure p 0 that
is
∫ T
s 0 c p (T )
= s 0 + dT. (1.17)
T 0
T
From this equation and Eq. (1.16) one obtains for s
( ) p
s = s 0 − R g ln , (1.18)
p 0
where s 0 depends only on T , once p 0 is selected.
5 See, i.e., Ref. [9] for complementary information and for discussion of the anomalies that appear in the
application of the Third Law.