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

VII.2 Solid tin oxides and hydroxides 123
[1941GAR/HEI] and [1942GOR/LEI] agree quite well with each other, but the result is
not very precise.
Figure VII-8: Solubility of SnO(cr) in HClO 4 solutions (: experimental data of
[1942GOR/LEI]; : experimental data of [1941GAR/HEI] (HCl); solid line:
ο
Δ (SnO, cr, 298.15 K) = − 253.11 kJ·mol –1
fGm
(this evaluation); dashed line:
ο
Δ (SnO, cr, 298.15 K) = − 254.509 kJ·mol –1
fGm
[1966MES/IRA]; dash dotted line:
ο
Δ G (SnO, cr, 298.15 K) = − 251.72 kJ·mol –1 ).
f
m
-1.2
log 10
(m Sn(II)
/mol·kg –1 )
-1.4
-1.6
-1.8
-2.0
-2.2
-2.4
-2.6
-2.8
exp.data
[1942GOR/LEI] [1941GAR/HEI]
log 10
*K° s0
(SnO, cr, 298.15 K)
1.756 [1966MES/IRA]
2.00
2.244
-3.0
-2.2 -2.0 -1.8 -1.6 -1.4 -1.2 -1.0 -0.8
log 10
(H ini
/mol·kg –1 )
Mesmer and Irani [1966MES/IRA] studied the solubility of high purity
SnO(cr) purchased from Baker and Adamson. These authors kept the ionic strength
constant (1.0 M NaClO 4 ) and measured the pH values of the equilibrated solutions. As
* ο
* ο
shown in Figure VII-9 a far more precise log10 K
s0
value was obtained ( log10 K
s0
=
(1.756 ± 0.100)). Surprisingly enough the standard Gibbs energy of tin(II) oxide
according to Mesmer and Irani’s solubility data is considerably more negative
ο
ΔfGm (SnO, cr, 298.15 K) = − (254.51 ± 0.51) kJ·mol–1 than that consistent with the
ο
ο
CODATA key value for Δ f H m (SnO, cr, 298.15 K) ( ΔfGm(SnO, cr, 298.15 K) =
− (251.91 ± 0.23) kJ·mol –1 ). Generally solubility data favour values indicative for more
soluble i.e. less stable phases.
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012