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

A Discussion of selected references
293
be concluded that the uncertainty is 1σ; in the recalculated values this is changed to 2σ.
The recalculated values are:
Δ
f
H
[1953KIN/TOD]
f
ο
m
(SnO, tetr., 298.15 K) = − (286.00 ± 1.34) kJ·mol –1 and
Δ H (SnO 2 , tetr., 298.15 K) = − (580.85 ± 0.67) kJ·mol –1 .
ο
m
This paper presents the results of low-temperature heat capacity measurements of both
tin(II) and tin(IV) sulphides using adiabatic calorimetry. Both compounds show normal
heat capacity curves, except that at temperatures below 80 K, SnS 2 has the lower molar
heat capacity.
The measured heat-capacity data of α-SnS listed in Table A-9 were
approximated by cubic splines, see Figure A-17. The extrapolated portions, between 0
and the first measured value, were evaluated by means of the empirical sum of Debye
(Eq. (A.30) and Einstein (Eq. (A.31)) functions with Θ = 146 K and Θ = 311 K.
D
Θ
3 D / 4 2
, D / 9( / D ) T y y −
= Θ e (e −1) d
0
2 2
, E / 3( E / ) exp( E / )/[exp( E / ) 1]
CV
R T
∫
y y
(A.30)
C R = Θ T Θ T Θ T − (A.31)
V
This sum fits the measured heat capacities to within 1% and for the temperature range
51 to 170 K, see Figure A-17.
The measured heat-capacity data of SnS 2 (cr) listed in Table A-10 were
evaluated analogously, but this time the sum of one Debye function with Θ D = 172 K
and two Einstein functions with Θ E1 = 369 K and Θ E2 = 415 K were employed for
ο
extrapolation from 0 to the first temperature where C p,m
has been measured. This sum
fits the measured heat capacities to within 1% and for the temperature range 51 to
170 K, see Figure A-18.
E
T/K
ο
C
p,m
/J·K −1·mol −1 T/K
Table A-9: Heat capacities of α-SnS.
ο
C
p,m
/J·K −1·mol −1 T/K
C
ο
p,m
−1
/J·K
−1·mol
52.45 19.924 114.7 36.974 216.37 46.442
56.82 21.401 125.28 38.698 226.05 46.819
61.4 23.117 136.01 40.196 236.31 47.196
65.9 24.769 146.22 41.426 246.03 47.572
70.49 26.263 155.93 42.384 256.19 47.907
75.28 27.711 166.03 43.263 266.05 48.325
80.2 29.179 176.12 44.099 276.36 48.576
83.71 30.158 186.09 44.727 286.68 48.911
94.67 32.920 195.91 45.355 296.8 49.246
104.47 35.012 206.31 45.815 298.15 49.246
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012