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

VII.2 Solid tin oxides and hydroxides 129
Gurevich et al. [2004GUR/GAV2] and [2004GUR/GAV3] measured the heat
capacity of SnO 2 (cass) in the temperature range of 13.4 to 336 K using an adiabatic
calorimeter. Two samples of tin dioxide with w(SnO 2 ) = 99.906 %(RP) and w(SnO 2 ) =
99.996 %(AA), respectively, were investigated, see Table A-70. They used the Debye-
Einstein-Kieffer equation to fit their experimental data (see Eq. (A.85)). The resulting
data on heat capacity and entropy are displayed in Table VII-5 and compared with a
conventional fitting equation which was conducted as follows.
Table VII-5: Comparison of thermodynamic data of SnO 2 (tetragonal) at 298.15 K.
[2004GUR/GAV2]
this review
o
C
p, m
/J·K –1·mol –1 55.24 ± 0.03 55.26 ± 0.09
ο
S
m
/J·K –1·mol –1 51.82 ± 0.07 51.77 ± 0.14
[ H ο ( T) − H
ο (0K) ]/kJ·mol –1
8.806 ± 0.005 8.805 ± 0.017
m
m
The first step was to examine up to which temperature the heat capacity of
SnO 2 (cr) obeys Debye’s T 3 ο
law, see Figure VII-11. In fact the first 17 C p,m
values of
[1980ZHO/KOS] and [2004GUR/GAV3] are within the experimental uncertainty
proportional to T 3 ο
and at 16 K the heat capacity ( (SnO 2 cr, 16 K) = 0.168
J·K –1·mol C p,m
–1 ) agrees closely with that derived by Gurevich et al. From T 0 = 16 K to
ο
336 K, Cp
,m ( T ) was approximated by Eq. (VII.25) containing 6 adjustable parameters
ο
(a to f ) whose numerical values refer to /J·K –1·mol –1 and T/K, see also Table A-73.
C p,m
ο
ο
[ C (T) – (T 0 )]/J·K –1·mol –1 = a [(T – T 0 )/K]+ b [(T/K) 2 – (T 0 /K) 2 p,m
C p,m
]
+ c [(T/K) –2 – (T 0 /K) –2 ] + d [(T/K) –3 – (T 0 /K) –3 ]
+ e [(T/K) –0.5 – (T 0 /K) –0.5 ] + f [(T/K) –1 – (T 0 /K) –1 ]
(VII.25)
a b c d e f
Eq. (VII.25) 1.7419×10 –1 – 2.1858×10 –4 – 2.9144×10 4 1.1389×10 5 – 1.0659×10 3 4.4830×10 3
ο
The uncertainty of C ( ) p,m
T
was estimated by
N
ο ο 2
∑ { Cp,m (obsd) − Cp,m(calc)}
ο 1
,m
=
sC ( p
)
N − 7
= 0.089 J·K –1·mol –1 .
Thermodynamic functions
T
ο
ο
m
= ∫ p,m
0K
S ( T) ( C / T)dT
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012