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

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X Group 15 compounds and complexes
Figure X-2: Extrapolation to I = 0 of the experimental data for reaction Sn 2+ +
2NO − Sn(NO 3 ) 2 (aq) in NaClO 4 media.
3
3
Sn 2+ + 2NO – 3 Sn(NO 3 ) 2 (aq)
2
log 10
β 2
+ 6D
1
0
0 2 4 6 8
I / mol·kg –1
X.2 Phosphorus compounds and complexes
X.2.1 Solid tin phosphide
Tin forms a ternary compound with silver, phosphorus and germanium with the formula
(Ag 6 Sn 4 P 12 )Ge 6 . The crystal structure is cubic in the space group I 43m (No. 217) with
lattice parameters a = 10.430(3) Å, Z = 2 [1976SCH/HAU], [1979HON/SCH],
[1980HON/SCH].
Gmelin et al. [1989GME/HON] determined the standard enthalpy of formation
using the heats of reaction data on (Ag 6 Sn 4 P 12 )Ge 6 (cr) 6 Ag(cr) + 6 Ge(cr) + 4 Sn(l)
+ 3 P 4 (g). They calculated the second and third law values using the elemental data
from Kubaschewski and Alcock [1979KUB/ALC] and obtained the following value:
f
ο
m
Δ H (Ag 6 Sn 4 P 12 Ge 6 , cr, 298.15 K) = − (147.0 ± 7.0) kJ·mol –1 .
Gmelin et al. [1989GME/HON] used an automated adiabatic calorimeter to
determine the specific heat in the temperature range from 2 to 100 K. Above 100 K,
they used a Perkin-Elmer DSC-2 scanning calorimeter; the errors in temperature were
less than 0.15 degree and in the calorimetric data, the errors were less than 1.5%. Their
ο
data from 230 to 320 K result in C (Ag 6 Sn 4 P 12 Ge 6 , cr, T )/J·K –1·mol –1 p,m
= (556.2 ± 8.7)
+ (0.3406 ± 0.0208) T/K − (2.572 ± 0.217) × 10 6 (T/K) –2 , leading to:
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012