2072
AFANAS’EV et al.
≠
0
ond process is the action of the electric field of ions on
the solvent and certain orientation of solvent moleꢀ
the molar concentration of the solution, mol/l;
E
is
η
the activation energy of viscous flow of the pure solꢀ
cules linked with ions [25]. These contributions
≠
el
vent; and
E
is the contribution of the electrolyte to increase as the temperature grows because of an
η
increase in kinetic energy. Since the density of charges
of the tetrafluoroborate and tetraethylammonium ions
is not large, the first process predominates.
It follows that the viscosity of our solutions is
largely determined by the destructuring of PC, which
the activation energy of momentum transfer.
It was shown that, according to (6), the activation
≠
energy of viscous flow of a solution (
E ) linearly
η
depended on the molar concentration
lyte (
tributions of the solvent and electrolyte to the activaꢀ
c of the electroꢀ
r
= 0.995). This allowed us to determine the conꢀ is characterized by very close packing of molecules
–
+
[
26], under the action of largeꢀsized Et N and BF4
4
tion energy of viscous flow of solutions of Et NBF4 in
4
electrolyte ions. As the concentration of Et NBF
propylene carbonate. These contributions were found
4
4
increases, this process is accompanied by an increase
in energy expenditures, whereas an increase in temꢀ
perature contributes to solvent destructuring because
of an increase in the kinetic energy of molecules.
≠
0
≠el
η
to be commensurate,
E
= 14.46 kJ/mol and
E
=
η
2
6.1 kJ/mol. This led us to conclude that, in agreeꢀ
ment with the transition state theory [21], viscous flow
of our solutions as electrolyte concentration increased
was largely determined by energy expenditures for solꢀ
vent destructuring with the formation of an additional
number of vacancies to provide conditions for jumps
of not only its own molecules but also the ions introꢀ
duced. Propylene carbonate is a mediumꢀstructured
solvent from the soꢀcalled gray zone (the Trouton conꢀ
stant is SV = 11.63, and the Kirkwood dipole orientaꢀ
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Negative values of the entropy of activation (
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g
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)
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4
4
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entropy of activation over the concentration range
studied. Note that solutions of Et NBF in PC are
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4
4
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ences (Wiley, New York, 1972; Mir, Moscow, 1976).
#
E
(=
Δ
H
)
values for systems with these two electroꢀ
η
lytes differ less significantly.
S# values are constant to within their estimaꢀ
The
tion errors ( 0.2 J/(mol K)) over the temperaꢀ
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39
,
Δ
1
σ
#
=
±
ΔS
,
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almost invariable structure of solvation complexes as
the temperature increases from 283.15 to 308.15 K.
According to the Eyring model [21], in the absence of
changes in interactions between ions and solvents, the
activation energy of viscous flow remains constant,
1
1
1
2. J. Barthel, M. Utz, K. Gross, and H.ꢀJ. Gores, J. Solut.
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η
concentration dependences.
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4
4
,
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 83
No. 12
2009