Handbook of Solvents - George Wypych - ChemTech - Ventech!

558 Y. Y. Fialkov, V. L. Chumak
Figure 9.22. Stability constant of amine complexes of
some Ni(NH 3) + in water-organic solvents: 1-NiEn 2+ ;
2-[N; NH 3] 2+ ; 3-[CdCH 3NH 2] 2+ ; 4-[AgCH 3NH 2] 2+ ;
5-[AgEn 2] 2+ ; 6-[NiEn 2] 2+ .
tion: ΔH=RT 2 (dlnK/dT) and ΔS = RlnK +
T(dlnK/dT) or ΔS =ΔH/T + RlnK. Because
equilibrium constant is a function of both
temperature and permittivity [9.52a], i.e.,
K = f( T,ε
)
[9.125]
A change of constant during temperature
change is a consequence of enthalpy of process
(not equal to zero) and temperature de-
pendence of permittivity. Thus, the change of equilibrium constant with temperature
changing depends on both self-chemical equilibrium characteristics (here ΔH) and solvent
characteristics (namely, solvent permittivity influence on equilibrium constant). This is pertinent
from Figure 9.23, which shows dependence of equilibrium constant logarithm on reciprocal
permittivity (isotherms). Equilibrium constants, obtained experimentally (dotted
linea-b)correspond to various values of permittivity.
The thermodynamic characteristics of a chemical process, calculated from equilibrium
constant polytherms, are integral characteristics (ΔH i and ΔS i), i.e., they consist of
terms related to process itself (ΔH T and ΔS T) and terms depended on permittivity change
with temperature changing (ΔH ε and ΔS ε):
ΔH = ΔH + ΔHε
[9.126a]
i T
ΔS = ΔS + ΔSε
[9.126b]
i T
Figure 9.23. Isotherms lnK - f(ε) for different temperatures
(T 1