Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 69
The following text was automatically extracted from the image on this page using optical character recognition software:
ENTROPIES OF INORGANIC SUBSTANCES AT 298.16 0K.
gas state). The sum is S294.25= 80.62 0.15 for the equilibrium
mixture of NO2(g) and N204(g).
At 294.250, the boiling point, S094.25= 57.34 for NO2(g) is calculated
from the data given previously. Giauque and Kemp find the degree
of dissociation to be a-=0.161, from a careful study of available
equilibrium data for the reaction N204=21NO2. By substituting this
value in the relationship,
1 2a 1-a 2aR 2a
S20o4=1 Smix-1 SO Rn + in
1-a -a 1+a 1-a I +-a
there is obtained S294.25= 72.50.2 for N204(g). This value corres-
ponds to Sl9s.16= 72.7 0.2.
Pentoxide.-An approximate value of the entropy of N205(c) may
be obtained from the heat-capacity data of McGraw (350) (950-245).
The extrapolation is large, as C,-14.27 at 950, and is subject to a
large uncertainty. There is calculated S2s8.16=36.62, of which 8.68
is extrapolation below 89.10.
An estimate of the entropy of N205(g) may be made by adding the
above result to the entropy of sublimation, ASs.98186-45.2 (270).
The result is So9s.,-82, which can be considered merely an order-of-
Nitric Acid.-Forsythe and Giauque (160) (130-3030) measured
the heat capacities of HNO3, HNO3.H20, and HNO3-3H20. Their
entropy calculations are adopted here.
For HNO3, there are obtained S'5.00=0.24 (extrapolation), S~31.51-
S5.oo=0019.45 (crystals), AS231.51=2,503/231.51 10.81 (fusion), and
S298.16-S31.51= 6.69 (liquid). The sum is S2",.=6-37.190.10 for
HNO3(1). To obtain the entropy of HNO3(g), there are added
ASgs.86- 9,355/298.16 31.38 (vaporization at 0.0828 atm. pressure)
and AS298.18= -4.95 (compression form 0.0828 to 1 atm. pressure).
The result is S298.1= 63.620.2 for HNO3(g).
Similarly for HNO3.H20, there are obtained S5.00o= 0.22 (extrapola-
tion), S235.48--S5.00o 23.64 (crystals), AS 35.48=4,184/235.48- 17.77
(fusion), and S s9.16- S35.48= 10.21 (liquid). The sum is S2s8.1s=51.84
0.1 for HNO3-H20 (1).
Also, for HNO3.3HO there are computed S05.00=0.37 (extrapola-
tion), S254.63-SO.00=43.23 (crystals), AS54.63= 6,954/254.63 27.31
(fusion), and S,8s. -S254.83=- 12.02 (liquid). The sum is S98s.16-82. 93
0.2 for HNO.3H20O (1).
Hyponitrous Acid.-Latimer and Zimmermann (322) estimated
S298.16= 52 for H2N202 (aq.).
Ions.-Latimer, Pitzer, and Smith (325) obtained S98s.= 35.00.2
for N03-(aq.) from thermal data for each of the following reactions:
KN03(c) -K+(aq.) +-NO--(aq.) and Ba(NO3)W(c)- Ba++(aq.) +
The same authors report S,.,1,=29.91.0 for NO2- (ag.) from
thermal data for the reaction AgNO(c)=-Ag+(aq.) +NO2- (aq.).
Latimer and Zimmermann (322) estimated S1,,,--34 for H2NO2
(aq.) and S9gs.,-6.6 for N202--(a.).
Nitrosyl Bromide.-Blair, Brass, and Yost (46) determined the heat
and free energy of the reaction 2NO (g) +Br2(g) =2NOBr(g). Their
Here’s what’s next.
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Kelley, K. K. Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation, report, 1950; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc12637/m1/73/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.