Chemical Thermodynamics of Tin - Volume 12 - OECD Nuclear ...

272
A Discussion of selected references
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m
TDB auxiliary data as well as S (Sn, β, 298.15 K) = (51.18 ± 0.08) J·K –1·mol –1 and
S (SnO, tetr., 298.15 K) = (57.15 ± 0.20) J·K –1·mol –1 selected by this review.
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m
The potential values measured with cell 1 result in
f
ο
m
Δ G (SnO, tetr., 298.15 K) = − (257.23 ± 0.67) kJ·mol –1 .
When the average potential-difference value of cell 2 measured at 318.07 K is
corrected for the new standard state pressure p° = 1 bar and extrapolated to 298.15 K
using the approximation
Δ G
f
ο
m
Δ G
r
ο
m
((A.17), 318.07 K) − Δ G
f
ο
m
ο
r m
((A.17), 298.15 K) = − ΔT Δ S
(SnO, tetr., 298.15 K) = − 253.66 kJ·mol –1 is obtained.
(A.17)
The mean value obtained with cells 1 and 2 (− (255.44 ± 1.78) kJ·mol –1 )
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overlaps with that derived from solubility measurements Δ fGm(SnO, tetr., 298.15 K) =
− (254.51 ± 0.57) kJ·mol –1 [1966MES/IRA].
[1929MIL2]
The heat capacities of Sn(II) and Sn(IV) oxide, lead dioxide and lead orthoplumbate
have been determined from 70 to 300 K and their entropies at 25 °C have been
calculated.
[1930RAN/MUR]
The equilibrium in the hydrolysis of SnCl 2 has been measured at 25 °C. The Gibbs
energy of the solid tin(II) hydroxide chloride, which was presumed to be
Sn(OH)Cl·H 2 O(s), and the activity coefficients of SnCl 2 and of Sn 2+ have been
calculated.
The data of Randall and Murakami have been carefully measured and
meticulously reported. They have been evaluated according to the 1930 state of the art,
which was set among others by Randall (see Table A-4).
Table A-4: Composition of tin(II) hydroxide chlorides [1930RAN/MUR].
Comp. Sn 21 Cl 16 (OH) 14 O 6 (cr)
abhurite
Sn(OH)Cl·H 2 O(s) Sn(OH)Cl(s) SnO(cr)
romarchite
Sn 6 O 4 (OH) 4 (cr)
hydroromarchite
w (Sn) 73.45% 62.75% 69.35% 88.12% 84.36%
w (Cl) 16.71% 18.74% 20.71%
w (O) 9.43% 16.91% 9.35% 11.88% 15.16%
w (H) 0.42% 1.60% 0.59% 0.48%
Unfortunately Sn(OH)Cl·H 2 O(s) was characterised analytically only and no
X-ray data were taken. A thermodynamic analysis of these solubility data using the SIT
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012