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

VIII.3 Aqueous halide complexes
185
Figure VIII-25: Species distribution curves of Sn(IV) chlorido complexes.
100
80
Sn 4+
SnCl 3+
SnCl 2
2+
SnCl 4
(aq)
SnCl 6
2–
% Sn 4+
60
40
SnCl 5
–
20
0
-6 -4 -2 0
log [Cl – ] TOT
The formation constants listed in Table VIII-10 have been used to extrapolate to
I = 0 by weighted linear regression and error propagation assuming Gaussian probability
distribution applying the Specific Ion interaction Theory (see Appendix A). The resulting
thermodynamic constants are also are listed in Table VIII-10. Obviously, the
extrapolation to I = 0 using data for I m ≥ 5.55 mol·kg –1 results in higher uncertainties than
predicted for the range of ionic strengths were the actual measurements were carried out.
Therefore, the authors preferred to define an additional key ionic strength within the
range covered. The interpolated formation constants at I m = 6.41 mol·kg –1 (5 M HClO 4 )
using weighted linear regression are also listed in Table VIII-10. The following
thermodynamic formations constants have been determined
ο
log10 β
1
((VIII.11), q = 1, 298.15 K) = (3.19 ± 0.50).
ο
log10 β
2
((VIII.11), q = 2, 298.15 K) = (5.95 ± 0.36).
ο
log10 β
4
((VIII.11), q = 4, 298.15 K) = (9.57 ± 0.32)
ο
log10 β
5
((VIII.11), q = 5, 298.15 K) = (10.93 ± 0.41).
ο
log10 β
6
((VIII.11), q = 6, 298.15 K) = (9.83 ± 0.49).
(for the corresponding Δε values see Appendix A).
The above listed selected thermodynamic formation constants correspond to
Δ G ((VIII.11), q = 1, 298.15 K) = − (18.2 ± 2.9) kJ mol –1 ,
r
r
ο
m
ο
m
Δ G ((VIII.11), q = 2, 298.15 K) = − (33.9 ± 2.1) kJ mol –1 ,
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012