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TitleEffect of pressure on the dissociation of electrolytic solution : I.Electrical conductivity of hexammine cobalt(III) : chloride athigh pressures
Author(s) Shimizu, Kiyoshi; Takizawa, Hideto; Osugi, Jiro
Citation The Review of Physical Chemistry of Japan (1963), 33(1): 1-5
Issue Date 1963-10-28
URL http://hdl.handle.net/2433/46830
Right
Type Departmental Bulletin Paper
Textversion publisher
Kyoto University
The Review of Physical Chemistry of Japan Vol. 33 No. 1 (1963)
cv, ~.OF
THE R£VISW OF PHYSICAL CHE64ISFAY 01. JwFA.w, VoL. 33, No. I, 1963
PRESSURE. ON THE DISSOCIATION OF ELECTROLYTIC
I. Electrical Conductivity of Hexammine Cobalt (III)
Chloride at High Pressures
BY 1lIYOSHI SHIMIZII, HIDETO TAxIZAWA AND ]IRO OSUGI
SOLUTION
From the equivalent conductivity, .I;oF dilute solution (1.Ox 10-<-,-1.Ox 10-3.~~ of [Ca(\Ha)s]Claat 23'C under high pressure up to 600kg/cm~, the degree of dis-sociation. a. and the dissociation constant, K, of _[Co(NHa)s]CI%' farmed between
[Co(vHs)s]3' and CI- Lace been determined. d increases with increasing pressure. n end K have the minimum values at about 400 kg/cm~ and the volume change, VV, caused by dissociation, are l7 tms/mole at 300 kg/cm'- and -13 cma/mole at 500 kg/cm2. The equivalent conductivity at infinite dilution, da, increases from 183.3 to 189.0 under pressure. This may be due to the increase of the ionic mobility which is related with [be viscosity of water. The increase of A, there-for4 may be mainly ascribed to the increase of ionic mobility under pressure.
i
Introduction
It. was shown by Hamann and Strausstl [hat the. ionization of-the simple electrolvtes were
enhanced at high pressures. From [he equivalent conduc[iciEes, d, of the dilute solutions under
high pressures, the variations of the degree of dissociation, a, the dissociation constant, K, and
the equivalent conductivity at infinite dilution, do, are determined, and aLo it is possible to
estimate the amount of the volume change, dF, due to [he dissociation o[ the electrolytes. The
authors have studied the ionic conductivity of the water solution of a complex, [Co(NH;~e]Cl„
at 25'C up to 600 kgJcm~ and examined the pressure edezr on a, K and do.
Experimentals
Hexammi¢e cobalt (III) chloride, (Co(NH,),;jCl„ was prepared from the water solution of robaltous chloride, ammonia, ammonium .chloride, and decolorizing charcoal as a catalyst by the
method of .Bjerrum and McReynolds2>. The crystals ware thoroughly washed with conductivity a~a[er and absolute alcohol, then dried to a constant weight at g0~100`C.
:1s show¢ in Fig. 1, the. conductivity cell made of te(lon, of capacity 25 ml and cell constant
0:322cm s, igas mou¢ted i¢ a high pressure vessel cortaining a thermocouple of chromef-alumel
as in the-previous papera). The solution, which was isolated with mercury in a glass cup from
(Received Augusl 1, 7963) I) S. D. Hamann and lV.$[rauss, Trans. Furadey Soc.; a`l, 1684 (1955)
1) w. C. Fernelius, lnorgonic Syntheses. II, p. 276 (1915) 11cGraw-Hill 3) &. Shimizu, Tlris lourrcel, 30, 73 (1960)
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i
K. 56imizu.
T G=G
asilicone oil, was compressed-by an of
Bourdon-type gauge. The pressure ves
The conductivity was measured at a t
cen[ra[ions of solution 1.0x10''•-1.Ox
of solutions under high pressures, it is
are available for the hexammine cobal
made in terms of thecompressibility
Resu
The equivalent conductivity, A, i
the equivalent conductivity is proporC
effects of pressure on the ionic mobilit
Fig. 3 shows the p1oLS of the equ
concentration, Ct/z, w•hic6 follows Foh
curves lie slightly below Onsager's the
ion-pair [Co(NH~,JCIz+ formed beta
Linhard and ilfonks>. Then, the ion-pai
and CI-:
[Co(NH,)e (1-a)n
where a is the degree of dissociation a
4) R. E, Cibson and 0: H. LoeRle 5) V. Jl. Linhard, Z. FJekfrochene.
I. L. Jenkins and C. D. Monk,
The Review of Physical Chemistry of Japan Vol. 33 N•
eu, H. Takizasvaand J.. Osugi ~ .
o -
Fig. t High pressure conductivity cell V :high pressure vessel
M : mercun-C 5 : solution C : tedon cell
S O: silicone oil G
G :glass Cup ~~ M T
c thermocouple
V
I injecto-. The pressures were measured by a calibrated set was. immered in a temperature bath of liquid paraffin. emperature 2i-C, at pressures 1600 kg/cmr and at con-
10-s .V. Tn order to calculate the equivalent conductivity
necessary to know [heir compressibility. No such data
t (III) chloride solutions and thus the calculations were
of water+l.
Its and Considerations
ncreases with increasing pressure as shown in Fig. 2. As tonal to ionic mobility a¢d the degree of ionization, the
y and degree of ionization should be examined. ivalent conductivity. ,1, against square root of equivalent
Lrausch~s empirical low. The experimental conductivity
oretical lines. This slight difference may be attributed to ~een [Co(NH~s]'* ion and CI- ion as pointed out by r [Co(NHa)fi]CF* would be in equilibrium with [Co(NHa)„]'*
]Clr* ̂ [Co(NHs)a]s* + Cl' r am (2+a)m
nd m is molar concentration. The equivalent conductivity
r. !. dm. Clrem. Soc., 63, 893 (1941) 59, 114 (1944) 1, Ckem. Soc., 19al, 68
w.
~;.
;.
~~-.^.
6
Effect of Pressure
The Review of Physical Chemistry of Japan Vol. 33 No. 1
on tLe Dissociation of Electrolytic Solution 3
(1963)
S ~
>so
<,~
12
'-~`
rre~ ' I Q~ o, ~ ~ ~ ° >m ~ a~
Fig..2 Pressure dependence of equivalent Fig. 3 Equivalent conductivity of ~ conductivity of [Co(NHs)s]Clr [Co(NH3~]Cls at two pres-
-~-: 1.Ox10-aN -0-~ lkg/cm2 -~-: 600 kg/cm2.
---: Onsager's theoretical line
is as follows,
r
where w is the solvent-corrected specific conductivity, Zs [he ion valency of ith ion, me the
concentration (g ion/1) and do the ionic conductivity.
Then,
dC= 3zXmO.[Co(VHa)a73' ~' SCI-) t 2(1-IX)m(.[[Co:\Ha)a7C1'*'i z1C1-)-
.. d=cYA"+ 3 [1-cr)ifz`=al\AOS,_ 3 ~ zr\_lbsr._ 3 bzt111M-y 2 (
where
~fCo~NH°)e]s* + aCl-= nsi = A0u _ bul`/2.~
Alcufi`Ha)e1cP• + .tcl- = Az1 = ~ z` - bz`I vz
and ionic strength, 1, is,equal to C(1+~).
In [his case, the ignic mobility of thebivalent ion-pair is taken as two-thirds of that of the
tervalent cation. Thedegree of dissociation,. a, is obtained from Fy. .(I) and the experimental values of d under pressures by means of successive approximation.
The dissociation constant, K, is represented by the following equation.
K={[CO(i\rH°)°}'*}.{Cl-}_~(2+a)mjjz (2)
where fr (1, 2, 3) are the activity coefficients of [Co(NH~°]'•, CI- and [Co(NH;)s]CIZ'. which
have been calculated from the Debye-Huckel equation,
i
eTh Review of Physical Chemistry of Japan Vol. 33 No. 1 (~ i
•~
4 K. Shimizu, H. aT kizawa and J. Osugi ~. •
-)ogf, 0.509 Ztz71/2:f
ca;~ .~The results are shown in Table 1, Figs. 4 and 3. As shown in figures, the degree ~
ra~.:
Table 1 A, a and /i under pressures .~
PIx IO-~:V 2x10-~N 3x 10"4N !:
(,kg/cm2) Aan x•lo3 a a F•lW A a K•107: ~3 •
1 183.3 179.5 0.9929 13 177.9 0.9896 1 i 176.fi 0.9859 18100 185.8 181.3 9.9859 6.3 l i9.i 0.9789 8.0 178.2 0.9754 t0
200 186.9 182.3 0.983fi 3.fi 180.4 0.9 i67 73 I i9.0 0.9119 8.7300 188.0 183.2 0.9813 4.8 18].3 0.9743 6.fi 179.8 0.9683 7.7 !~400 188.7 183.9 0.9813 4.7 181,9 0.9 131 fi.3 180.3 0.9660 7.2
3W
6~
189.0
189.0
184.2
184.3
0.9613
0.9823
a.e
s. ~
182.3
182.3
0.9741
0.9140
6.6
6.6
180.8
180.9
0.9683
0.9691
7.8
8.1
P (kg/cmZ) A
5 x 10-+N
K K• 10~ A
8xt0-+1'
n K•10~
10 x 10'~ N
A a K•IW
goo
zoo
300
400
500
600
174.7
175,8
176.7
177.3
177.8
V 8.4
178.7
0.9823
0,9654
0.9629
0.9570
0.9546.
0.9581
0.9617
21
IC
10
8.9
8.4
9.0 10
nz.a
173.3
174.1
154.6
171.0
175.1
175.8
0.9768
0:9572
0.9533
0.9462
0.9426 0.9449
0.9483
26
13
l2
ll
]0
ll
11
171.2
171.9
1)2,fi
173.0
173.5
113:9
174.4
0.9749 0.9527 0.9477 0.9390 0.9367 0.9376 0.9435
28
IS
13
ll
11
I1
I2
i QM
ass
OW
e
DD
O
0
Fig. 4 Pressure dependence of degree of dissociation of [Ca(\H~)sJCh
-Q-: 1.0 x 10-~ N -~-; 2.0 rr
-~-: 3.0 n '~: 5.0 n -(}-: 8.0 n -~-: 10.0 0
Presave. k¢~'cm'
sociation
kg Jcma.
according
of each solution and the
The pressure coefficient
to the thermodynamical
dissociation constaet have
of In K gives. the volume
relation as Follows,
the minimum values at
change, dV, due to the
about 400
dissociation
I
I
Effect of Pressure
The Review of Physical Chemistry of Japan Vol. 33 No. 1
on the Dissociation of Electrolytic Solution 5
loo
:~
~~ Fig. 5 Pressure dependence of -:~ log lie/Xt of [Cd~rk7Clo
. ieo
oe aw .oo sm Pressure, ka/vn'
r71nKl _dV ~4) 8P /r RT'
dV are l7 cm'/mole at 300kg/cmo and -13cm~/mole a[ SOOkg/cm2, the sign of d1' changing
from positive to negative at about 400 kg/cmz. dV may be equal to dVt+dVr. dVr is the
volume change of ions themselves and positive in this system. dV, is the volume change of
sohent attracted by ions under pressures and negative because of [heincrease of ionic valencies:
dVt would be predominant at lower pressure so that dV is positive. At higher pressure, dT',
would take place of dV„ for wateq of which the dielectric constant increases with increasing
pressures, would 6e attracted much more by ions. Then pressure would favour the dissociation of ion-pair to ration and chloride ion.
~.m
~,.w
Fig. 6 Pressure dependence of equivalent conductivity at infinite dilution of [Co(NHa)s]Cla and viscosit}' of water
-~-: >I°/yr at 23'C (Cohen) -~-: i at 30'C (Bridgmanj
osso wo ~
Pressure. kg'an'
The equivalent conductivity at the infinite dilution, At, increases from 183.3 to 189.0 with
increasing pressure as shown in Table L This may be due to the increase of the ionic mobility,
which is related with the viscosity of water. rl. The variation of d, and p by pressure hate
similar tendencies as shown in Fig. 6. although R'alden's rule is not best obeyed by this electrolyte.
The increase of ~ by pressure, therefore, may be mainly ascribed to the increase of ionic mobility.
The authors have great pleasure in expressing their sincere thanks to the Department of
Education [or the Granb in Aid for Fundamental Scientific Research.
The Laboratory of Physical Chemistry
Kyoto University
Kyoto, Japan
6) B. K. P. Scaifc, Pror. phys. Sor., BfiB, i90 (1955)
(1963) i
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