Contributions to the Data on Theoretical Metallurgy: [Part] 11. Entropies of Inorganic Substances: Revision (1948) of Data and Methods of Calculation Page: 27
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ENTROPIES OF INORGANIC SUBSTANCES AT 298.160K.
polated portion below 3.160 is 0.005. The estimated error is large
because the data of Anderson and of Bronson and MacHattie cannot
be connected to those of Keesom and van den Ende in a reasonable
manner. It appears likely that a transition ("hump") may occur in
the temperature range 200 to 600, especially in view of the fact that the
entropy value is so low compared with that of Pb(c). The computed
result is a compromise.
The entropy of Bi(g) computed from the Sackur equation with R
In 4 added because of the quantum weight 4 (364) of the lowest energy
level is S98,1=44.68 0.01.
Almy and Sparks (7) have obtained the internuclear distance of
the Bi2(g) molecule as 2.85 X 10-8 cm., and the vibration frequency as
= 173. The nuclear separation results in I-=1,409 X 10-40, which, in
turn, yields S1+r,298.16=62.99. The vibrational entropy is Sv,298.168
2.40, and the sum is S298.16= 65.4 0.2.
Oxide.-Anderson's (11) (600-2900) heat-capacity data for Bi203(c)
lead to the values, S;6.2=6.22 (extrapolation) and S9.16 -S86.2= 29.96
(measured), making S98s.16=36.2 0.6.
Bromide.-Molecular-constant data estimated by Stevenson (467)
lead to S98.16=63.60.5 for BiBr(g).
Chlorides.-The BiCl3(g) molecule was considered by Howard and
Wilson (217), who gave 96(2), 130(1), 242(2), and 288(1) as the vibra-
tion frequencies, 2.46 X 10-s80 cm. as the Bi-Cl distance, and 930 as
the bond angle in the pyramidal model. From the last two figures
I-=740 X 10-40 and I2= I3=580X 10-40. The moments of inertia and
the symmetry number 3 result in S,+,298.16=70.27. The vibrational
entropy is SV,298.16-- 15.08. For BiC13(g), therefore, S 98.16- 85.3 1.0.
The heat and free energy of vaporization of BiC13(1) were obtained
formally from vapor-pressure data as AH298.16-=23,177 and AF298.16 =
12,228 (270). These correspond to AS298.16=36.52. The heat of fu-
sion of BiC13(c) at its melting point, 4970, was computed as AH497=
2,600 from binary-system freezing-point data (271). If it is assumed
that AC,=4 for the reaction BiC13(c) =BiCl13(), then AS'9s, 6=3.16 for
the fusion process. The entropy of sublimation is, therefore, AS298.16-
39.7. From this and the entropy of the gas there is obtained
S298.16=45.6+2 for BiCl3(c).
From molecular-constant data (467), there is computed S298.16=
60.9 0.5 for BiCl(g).
Sulfide.-Kelley (273) has obtained S8 .16= 33.8 for Bi2S3(c) from
data for the reaction Bi2S3 (c) 3H2(g) = 2Bi(c) + 3H2S(g).
Hydrides.-Molecular-constant data (212, 311) for BiH(g) and
BiD(g) yield, respectively, S9os.16=51.28 0.10 and Ss98.16=52.69
Iodide.-Stevenson (467) has estimated molecular-constant data for
BiI(g), which lead to S98.16=65.40.5.
Element.-From heat-capacity measurements of B4C(c) (281) and
a comparison of available entropy data for carbides with those of
their constituent metals there is estimated S2,s.= --1.7 0.2 for B(c).
Spectroscopic data for B(g) (311) show that, in obtaining the en-
tropy at 298.160 K., only two energy levels, having a separation of
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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/m1/31/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.