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

VII.2 Solid tin oxides and hydroxides 127
of the enthalpy, we have taken the average of the enthalpy data from the five low values
[1966MES/IRA], [1953HUM/OBR], [1942GOR/LEI], [1941GAR/HEI] and
[1929MAI], see Table VII-3.
Table VII-4: Previous critical evaluations of the thermodynamic data for SnO(cr).
ο
Δ fHm
/kJ·mol –1 ο m
S /J·mol –1·K –1 C ο p,m
/J·mol –1·K –1 Reference
− 280.71 ± 0.20 57.17 ± 0.30 47.78 ± 0.30 CODATA
− 280.68 ± 0.17 57.167 ± 0.291 [1987LAM/HIL]
− 280.71 ± 0.21
[1991GUR/VEY]
The selected heat capacity and entropy given below are based on Eq. (VII.15)
ο
and the linear regression of T, C p,m data between 263 ≤ T/K ≤ 311, see Appendix A
entry on [1978KOS/SAM], respectively.
ο
S m (SnO, cr, 298.15 K) = (57.18 ± 0.22) J·mol –1·K –1 ,
ο
C p,m (SnO, cr, 298.15 K) = (47.76 ± 0.08) J·mol –1·K –1 .
Analysis of the solubility data (see Table VII-3, Section VII.2.2.3) clearly
establishes that the following value of enthalpy should be selected:
ο
m
Δ fH (SnO, cr, 298.15 K) = − (284.24 ± 0.76) kJ·mol –1 .
This selection yields:
ο
Δ G m
(SnO, cr, 298.15 K) = − (255.44 ± 0.76) kJ·mol –1 .
f
VII.2.3
SnO 2 (cr)
VII.2.3.1
Enthalpy of formation of SnO 2 (cr)
Lavut et al. [1981LAV/TIM] determined the enthalpy of formation of oxides using a
combustion calorimeter. The enthalpies of formation of the oxides were calculated from
the reactions:
ο
f H m
β-Sn + O 2 (gas) SnO 2 (tetragonal)
SnO(tetragonal) + ½ O 2 (gas) SnO 2 (tetragonal).
The value of the standard enthalpy of formation of SnO 2 (tetragonal), is
Δ (SnO 2, tetragonal, 298.15 K) = − (577.63 ± 0.16) kJ·mol –1 .
There are several determinations of the standard Gibbs energy of formation of
SnO 2 (tetragonal) over the temperature range 673 to 1373 K using electrochemical
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012