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

VIII.1 Halide compounds
145
Figure VIII-5: Another plot of the standard molar heat capacity of SnCl 2 (cr).
Experimental data of Paukov et al. [1979PAU/STE] fitted using tension spline (10);
cubic spline fit leads to essentially the same result. The plot shows C
ο,m / p
T plotted
against T.
0.7
0.6
(C o p, m · T –1 ) / (J·K –2·mol –1 )
0.5
0.4
0.3
0.2
0.1
0.0
0 50 100 150 200 250 300
T / K
The selected heat-capacity and entropy values are from the analysis of the data
of [1979PAU/STE], as shown in Figures VIII-1 to VIII-5.
ο
–1
C
p,m
(SnCl 2 ,cr, 298.15 K) = (77.96 ± 0.31) J·K
–1·mol
ο
S
m
(SnCl 2 ,cr, 298.15 K) = (133.96 ± 0.53) J·K –1·mol –1 .
From these selected values, the Gibbs energy of formation of SnCl 2 (cr) is
calculated to be:
Δ G (SnCl 2 ,cr, 298.15 K) = − (286.07 ± 2.20) kJ·mol –1 .
f
ο
m
VIII.1.2.2 SnCl 2·2H 2 O(cr)
Tin(II) chloride dihydrate is a solid with a layered structure. It melts at 313 K.
Matsuo et al. [1974MAT/OGU] measured calorimetrically the heat capacity of
SnCl 2 ·2H 2 O crystals from 13 to 300 K. There is a phase transition at 217.94 K, which
complicates the measurement at 298.15 K. The solid of high purity was prepared from a
slowly cooled melt with a nearly stoichiometric content of water. The overall accuracy
of the measurement is estimated as 1% at 20 K and less than 0.3% above 50 K. The data
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012