Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 50
The following text was automatically extracted from the image on this page using optical character recognition software:
50 CONTRIBUTIONS TO DATA ON THEORETICAL METALLURGY
(crystals), AS273.18= 1,435.7/273.16= 5.26 (fusion), and S298.16- S273.18=
1.58 (liquid). The sum is S298.16= 15.94. This value is not the quan-
tity to be used in thermodynamic calculations, however, but it must
be corrected by adding R In 6/4=0.81, according to Pauling (385)
(see below). This makes S~os.l= 16.75+0.03 for H20(l).
For H20(g), Gordon (196) has computed S9s.16=45.10 from spec-
troscopic data and Giauque and Archibald (173) have made a small
correction to this value, raising it to 298.168=45.13. The latter also
obtained S98s.16=45.10 from their study of the reaction Mg(OH)2(c)=
MgO (c) +H20 (g). Other reported values are S98s.1 = 45.19, from ther-
mal data for the reaction H2(g) + HgO(c) =Hg(l) + H20 (g), and S98s.18 -
45.1, from thermal data for the reaction 2HC1 (g) + 1/2 02(g) = H20 (g) +
C12 (g) ,both obtained by Giauque and Ashley (174). The values of the
molecular constants assigned by Dennison (124), 1=1.023X10-4,
12- 1.921 X 10-40, 13= 2.944 X 10-40, e= 3,825, 2- 1,654, and 03= 3,936,
lead to S98s.1s=45.08. The value adopted for H20 (g) is Ss.98.18=45.13 +
The adopted value of H20(g) may be used to obtain an independ-
ent result for the entropy of H20(l). First, there must be added the
entropy of expansion, ASs9.18= 6.886, from 1 atm. pressure to 2.3756
cm. pressure, that is, the vapor pressure of H20(1) at 298.160. Second
there must be subtracted the small entropy correction, AS298.16=0.002,
for the difference between the ideal and actual gas. Third, there
must be subtracted the entropy of vaporization at 2.3756 cm. pres-
sure at 298.160, AS298.18=10,514/298.16=35.263. The net result is
S298.16= 16.75 for H20(l), which is in exact agreement with the third-
law value and constitutes excellent proof of Pauling's (385) correction
for randomness of the hydrogen bonds in ice crystals.
Heat-capacity measurements of D20 at low temperatures were
made by Brown, Barnes, and Maass (64, 65) (2030-2730), Cockett
and Ferguson (109) (2840-3260), and Long and Kemp (339) (140-
2960). The results of the last investigators will be employed. There
are computed S5.o=0.09 (extrapolation), S278.98-S15.0-=10.29 (cry-
stals), AS278.98=-- 1,501/276.98= 5.42 (fusion), and S298.168-S276.98 *1.47
(liquid). The sum is S29s.16 =17.27, to which must be added Pauling's
(385) correction 0.81, making S98.1s=18.08+0.10 for D20(l).
The entropy of D20(g) may be obtained from molecular-constant
data as listed b Long and Kemp, I ,=5.752X 10-40, I2=3.812X 10-40
13=1.790X10- o, -w1=2,784, w2=2,666, and w3=1,179. These values
give S!+r,298.1=47.288, So,29s.1 = 0.045 and S29s.18=47.33 0.10.
This value is adopted.
Returning now to Long and Kemp's heat-capacity measurements,
calculation gives S273.16=11.04 for D20(c), after applying the Pauling
correction. Long and Kemp have computed the entropy of sublima-
tion (3.65 mm. pressure) as AS273.16=12,636/273.16=46.26 and the
entropy of compression to 1 atm. pressure as AS273.16= -10.61. These
figures result in S273.1 =46.69 for D20(g). Heating the gas from
273.160 to 298.160 requires AS=0.71, so that S209.8.16=47.40. The
excellent agreement with the calculation from molecular-constant
data again substantiates the Pauling correction.
The entropy of HDO(g) may be approximated by adding R In 2
to the mean of the entropies of H20(g) and D20(g). The result is
S298.16= 47.6 0.2.
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/m1/54/: accessed April 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.