Influence of the temperature on heat effects of acid-base interactions in aqueous solutions of succinic and tartaric acids

Article abstract of DOI:10.1134/S0036024407060131

The heat effects of interactions of solutions of succinic and tartaric acids with solutions of HNO₃ and KOH or LiOH are measured over the temperature range 288.15-308.15 K at ionic strengths of 0.5, 1.0, and 1.5 (KNO₃ or LiNO₃). The heat effects of dissociation of the acids are calculated using a Pentium-150 PC with HEAT and RRSU universal software packages. The thermodynamic characteristics of the processes of stepwise dissociation of the oxyacids are determined. The influence of the temperature on the heat effects of the processes of stepwise dissociation of succinic and tartaric acids is discussed. Nauka/Interperiodica 2007.

Full text of DOI:10.1134/S0036024407060131

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2007, Vol. 81, No. 6, pp. 910–916. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © L.A. Kochergina, V.P. Vasil’ev, D.V. Krutov, O.N. Krutova, 2007, published in Zhurnal Fizicheskoi Khimii, 2007, Vol. 81, No. 6, pp. 1044–1050.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Influence of the Temperature on Heat Effects of Acid–Base
Interactions in Aqueous Solutions of Succinic and Tartaric Acids
†
L. A. Kochergina, V. P. Vasil’ev , D. V. Krutov, and O. N. Krutova
Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
e-mail: kochergina@isuct.ru
Received April 18, 2006
Abstract—The heat effects of interactions of solutions of succinic and tartaric acids with solutions of HNO3
and KOH or LiOH are measured over the temperature range 288.15–308.15 K at ionic strengths of 0.5, 1.0, and
1
.5 (KNO or LiNO ). The heat effects of dissociation of the acids are calculated using a Pentium-150 PC with
3 3
HEAT and RRSU universal software packages. The thermodynamic characteristics of the processes of stepwise
dissociation of the oxyacids are determined. The influence of the temperature on the heat effects of the pro-
cesses of stepwise dissociation of succinic and tartaric acids is discussed.
DOI: 10.1134/S0036024407060131
A great body of data on ionization constants of suc-
cinic and tartaric acids are available from the literature
Data on heats of dissociation of succinic acid are
available from [1, 7, 17, 19, 20]. ∆H° values deter-
1
[1–17]. The data were obtained at different ionic
mined from calorimetric measurements in [19, 20] dif-
strengths with supporting electrolytes of different
nature. We calculated weighted average values of ion-
ization constants for all ionic strengths. The data for
each of the acids were treated in terms of the equation
with a single individual parameter [18]:
fer by more than 2 kJ/mol. According to [19], ∆H =
1
2
.81 kJ/mol (T = 298.15 ä, I = 0.01, äNé background
3
electrolyte). According to [20], ∆H = 5.79 kJ/mol (T =
1
2
98.15 ä, I = 0.1, N‡ëlé background electrolyte).
4
∆
H° values determined from calorimetric data [19, 20]
2
Ò
2
1/2
1/2

K = K° – ∆Z A(I /(1 + 1.6I ) + bI,
(1)
and estimated from temperature coefficients of ioniza-
tion constants (at several temperatures and background
electrolyte concentrations) [1, 7, 17] differ even in sign.
Heats of stepwise dissociation of tartaric acid are avail-
Ò
where K and K° are negative logarithms of the con-
centration and thermodynamic ionization constants,
2
∆
Z is the difference of squared charges of reaction
products and initial components, A is the constant of the able from [21]. Unfortunately, ∆H
°
and ∆
H°
were
1
2
Debye–Hückel theory, I is the ionic strength of the estimated only indirectly from temperature coefficients
solution, and b is an empirical coefficient.
of dissociation constants of tartaric acid (∆H° =
1
Results of the treatment led to expressions relating
concentration ionization constants to the ionic strength
of the solution. Specifically for tartaric acid,
3
.1 kJ/mol, and ∆H° = –0.99 kJ/mol).
2
The aim of this work is the investigation of the influ-
ence of the temperature on the heat effects of dissocia-
tion of succinic and tartaric acids through the experi-
mental determination of enthalpies of ionization of the
oxyacids in aqueous solutions at temperatures of
c
1
1
/2
1/2


K = 3.03 – 1.018(I /(1 + 1.6I ) + 0.113I, (2)
c
1
/2
1/2
K = 4.38 – 2.036(I /(1 + 1.6I ) + 0.116I. (3)
1
2
0
88.15, 298.15, and 388.15 K and ionic strengths of
.5, 1.0, and 1.5 (potassium or lithium nitrate back-
Using Eqs. (2) and (3), we calculated ionization
ground electrolyte) and the calculation of thermody-
namic characteristics of processes of stepwise dissoci-
ation of the acids.
constants of tartaric acid: K = 2.60 and 2.73, and
1

K = 3.65 and 3.77 (for I = 0.5 and 1.5, respectively).
2
In the same way, we calculated thermodynamic ioniza-
tion constants for succinic acid: K° = 4.21, and
1
EXPERIMENTAL

K° = 5.64. The data obtained were used for calculat-
2
Reagent (“kh.ch.”) grade, crystalline succinic
ing constants at fixed ionic strengths required of calori-
metric data processing.
(
ç Suc) and tartaric (ç í‡rt) acids were used. Accord-
2 2
ing to data of potentiometric titration with KOH, the
acids were 99.90% pure. Carbonate-free solutions of
†
Deceased.
9
10

INFLUENCE OF THE TEMPERATURE ON HEAT EFFECTS OF ACID–BASE INTERACTIONS
911
Suc2–
KOH and LiOH and an HNO solution were prepared
α
H Suc
3
2
by the standard procedure [22]; regent (“kh.ch”) grade
substances were used. Concentrations of the solutions
were determined by standard titration methods [22].
Required ionic strength values were maintained with
the use of potassium nitrate and lithium nitrate. High-
purity (“ch”) grade potassium nitrate was recrystal-
lized, and accurately weighed portions were used for
solution preparation. Reagent (“kh.ch.”) grade LiNO3
was used; the solution concentration was determined by
ion-exchange chromatography: the solution was passed
1.0
0
.8
0.6
.4
HSuc–
0
+
through KU-2 cation exchanger in the ç form, and the
0.2
0
concentration of liberated hydrogen ions was deter-
mined by alkalimetry. The heat effects were measured
on an isothermal-shell calorimeter with automatic
recording of temperature–time curves [23].
2
4
6
8
10
12
14
pH
From the diagram of equilibriums in a succinic acid
aqueous solution (Fig. 1), it is seen that there is no pH
range with one of the stepwise dissociation processes
occurring singly. Therefore, the overall heat effect of
Fig. 1. Diagram of equilibria in a succinic acid aqueous
solution at 298.15 K and I = 0.0.
2
–
–
protonation of Suc and çSuc was measured. In this
–
2–
ments, degrees of protonation of HSuc and Suc varied
from 2 to 98% and from 26 to 99.9%, respectively. We
also determined the heat effects of dilution of succinic
acid solutions (pH 7.14, cSuc = 0.4818 mol/kg) with
background electrolyte solutions with pH 7.14. The
measurements were carried out at the three ionic
case, test conditions were selected so that one of the
2–
–
processes of protonation of Suc and çSuc dominates
the other in mixtures of solutions placed in the calori-
metric vessel in all series of thermochemical measure-
ments. We measured the heat effects of interactions of
succinic acid solutions neutralized to pH 6.8–7.14
strength values I = 0.5, 1.0, and 1.5 (KNO ) and tem-
(
cSuc = 0.4818–0.4836 mol/kg) with nitric acid solu-
3
tions of different concentrations (from 0.001 to peratures of 308.15 and 318.15 K.
0
.015 mol/l). The mineral acid solution was placed into
The measurement procedure was analogous to that
used previously [24] in the investigation of processes of
acid–base interaction in succinic acid aqueous solu-
the calorimetric vessel, and an accurately weighed por-
tion of the succinic acid solution with pH = 7.14, into
in
the ampoule. Test conditions were selected so that pH
of the mixture of the solutions (pH ) was in the range tions at 298.15 K. The experimental data listed in
fin
between 5.6 and 2.1. In this case, in a series of experi- Tables 1 and 2 were used for calculating heats of ion-
Table 1. Heats of interaction of a K Suc solution (0.4818 mol/kg) with HNO solutions (c = 0.0009–0.0130 mol/l) at T =
2
3
3
08.15 K
–
3
c × 10 ,
m, g
∆H
m, g
∆H
m, g
∆H
mol/l
I = 0.5
I = 1.0
I = 1.5
0
1
3
4
6
8
9
.973
.867
.204
.540
.321
.121
.423
0.49645
0.49965
0.50100
0.5004
–
0.011
0.08/5
0.235
0.535
–
0.49225
0.50320
0.49485
0.49470
–
0.075
0.369
0.712
1.175
–
0.50315
0.50280
0.49900
0.50595
0.49240
0.5033
0.118
0.487
0.541
1.5985
2.459
3.161
3.936
4.693
5.146
5.694
0.49750
0.49910
0.50135
0.50330
0.50015
1.903
2.242
2.652
3.032
3.564
0.50415
0.50680
–
3.012
3.505
–
0.50715
0.4955
1
1
1
0.310
1.18
2.95
0.50550
0.50420
4.294
4.977
0.49575
0.50265
Note: c is the concentration of HNO , m is the mass of K Suc, and ∆H, kJ/mol = ∆dilH – ∆mixH.
3
2
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 6 2007

9
12
KOCHERGINA et al.
Table 2. Heats of interaction of a K Suc solution (0.4818 mol/kg) with HNO solutions at T = 318.15 K
2
3
–
3
c × 10 ,
m, g
∆H
m, g
∆H
m, g
∆H
mol/l
I = 0.5
I = 1.0
I = 1.5
1
2
4
6
8
9
.220
.353
.614
.874
.032
.165
0.5025
0.4988
0.5001
0.50445
0.50445
0.49785
0.50115
0.4965
–
–0.039
–0.183
–0.353
–0.283
0.193
0.628
0.995
1.432
–
–
–
0.5020
0.50275
0.5020
0.49685
–
0.059
0.270
0.758
1.475
–
0.5002
0.49675
0.50340
0.491615
0.5035
0.49995
0.50395
0.500
0.011
0.349
0.762
1.489
1.975
2.397
2.519
2.669
2.959
3.224
0.5031
0.50415
0.498575
0.50181
–
2.514
3.218
3.905
4.076
–
1
1
1
1
1
0.34
1.37
2.54
3.63
5.86
0.49725
0.49975
1.435
1.507
0.50275
0.50345
0.5045
4.467
Note: See Table 1.
Table 3. Thermodynamic characteristics of the processes of stepwise dissociation of succinic acid
T
pK°
∆G°, kJ/mol
∆rH°, kJ/mol
–∆S°, J/(mol K)
– ∆G° , J/(mol K)
p
–
+
H Suc = HSuc + H
2
2
88
98
08
4.21 ± 0.01
4.19 ± 0.01
4.191 ± 0.01
24.02 ± 0.6
24.71 ± 0.6
25.51 ± 0.6
3.43 ± 0.30
2.19 ± 0.30
69.0 ± 0.9
73.1 ± 0.9
77.3 ± 0.9
126 ± 21
174 ± 21
2
3
0.90 ± 0.30
2–
HSuc = Suc + H+
–
2
2
3
88
98
08
5.64 ± 0.01
5.651 ± 0.01
5.67 ± 0.01
32.18 ± 0.6
0.44 ± 0.30
–1.57 ± 0.30
–3.07 ± 0.30
106.3 ± 0.9
113.2 ± 0.9
118.2 ± 0.9
33.32 ± 0.6
34.52 ± 0.6
Table 4. Heats of interaction of a Li Tart solution (1.2916 mol/kg) with HNO solutions at T = 288.15 K
2
3
c, mol/l
m, g
∆H
m, g
∆H
m, g
∆H
I = 0.5
I = 1.0
I = 1.5
0
0
0
0
0
0
0
0
0
0
.00441
.00685
.01054
.01299
.01666
.01911
.02278
.02820
.02885
.03251
0.50430
0.49615
0.50025
0.50060
0.49800
0.50365
–
1.105
1.693
2.861
3.439
4.010
5.147
–
0.50240
0.49745
0.50295
0.49470
0.49855
0.49910
0.50305
0.50160
0.499990
0.50380
1.034
1.750
2.914
3.640
4.710
5.417
6.222
6.953
7.759
8.409
0.500095
0.50525
0.50675
0.500060
0.50010
0.50165
0.50690
0.49685
0.49710
0.502025
1.012
1.726
2.931
3.766
4.943
5.506
6.519
7.283
8.028
8.619
0.50375
0.49835
0.49500
6.737
7.577
8.129
Note: c is the concentration of HNO , m is the mass of Li Tart, and ∆H, kJ/mol = ∆dilH – ∆mixH.
3
2
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 6 2007

INFLUENCE OF THE TEMPERATURE ON HEAT EFFECTS OF ACID–BASE INTERACTIONS
913
Table 5. Heats of interaction of a Li Tart solution (1.2916 mol/kg) with HNO solutions at T = 308.15 K
2
3
c, mol/l
m, g
∆H
m, g
∆H
m, g
∆H
I = 0.5
I = 1.0
I = 1.5
0
0
0
0
0
0
0
0
0
0
.00441
.00685
.01054
.01299
.01666
.01911
.02278
.02520
.02885
.03251
0.50175
0.49690
0.49830
0.49850
0.50005
0.50200
0.49905
0.49560
0.50430
0.49920
0.371
0.470
0.920
1.125
1.685
1.985
2.472
2.759
2.975
3.448
0.49705
0.49845
0.50145
0.50035
0.49800
0.49910
0.50315
0.49835
0.49605
0.50215
0.418
0.658
0.028
1.499
2.079
2.548
3.116
3.465
3.809
4.132
0.50051
0.50150
0.50340
0.50025
0.49900
0.50265
0.50120
0.49750
0.50505
0.50415
0.644
1.030
1.643
2.083
2.756
3.244
3.871
4.199
4.759
5.182
Note: c is the concentration of HNO , m is the mass of Li Tart, and ∆H, kJ/mol = ∆dilH – ∆mixH.
3
2
Table 6. Thermodynamic characteristics of the processes of stepwise dissociation of tartaric acid
T
pK°
∆G°, kJ/mol
∆rH°, kJ/mol
–∆S°, J/(mol K)
– ∆G° , J/(mol K)
p
–
+
H Tart = HTart + H
2
2
88
98
08
3.06 ± 0.01
3.04 ± 0.01
3.02 ± 0.01
16.87 ± 0.6
17.34 ± 0.6
17.81 ± 0.6
5.42 ± 0.30
4.06 ± 0.30
39.8 ± 0.9
44.6 ± 0.9
50.0 ± 0.9
151 ± 21
190 ± 21
2
3
2.41 ± 0.30
2–
HTart = Tart + H+
–
2
2
3
88
98
08
4.39 ± 0.01
4.38 ± 0.01
4.37 ± 0.01
24.21 ± 0.6
2.89 ± 0.30
1.04 ± 0.30
–0.85 ± 0.30
74.04 ± 0.9
80.3 ± 0.9
86.4 ± 0.9
24.99 ± 0.6
25.77 ± 0.6
ization of oxyacids such that the following function is obtained stepwise ionization constants of succinic acid
at a minimum:
are listed in Table 3.
n
Stepwise ionization constants of tartaric acid are
also too close to each other to allow for independent
exp
i
calc
i
2
F =
(∆ H – ∆ H )ωi
min,
(4)
∑
r
r
determination of heats of dissociation of ç í‡rt.
2
i = 1
Therefore, the overall heat effect of protonation of
2
–
–
where ∆ H
is the measured heat effect;
r
exp(i)
í‡rt and çí‡rt was measured. In this case, the pro-
portion of each of the stepwise protonation processes
was varied through a maximum range in going from the
first experiment to the last in each series. We measured
the heat effects of interactions of the dissociation prod-
ucts of tartaric acid with nitric acid solutions. Accu-
–
2–
∆rHcal = (∆[OH ]∆ H + ∆[Suc ]∆ H
1
r
w
r
(5)
–
+
∆[HSuc ]∆ H )/c° ,
r 2 Suc
–
2–
–
∆
[OH ], ∆[Suc ], and ∆[HSuc ] are the differences of
final and initial equilibrium concentrations of respec-
tive species; c°Suc is the total concentration of succinic
rately weighed portions of nitric acid (cHNO3
=
2
.140 mol/kg) were placed into the ampoule, and neu-
tralized solutions of tartaric acid of different concentra-
acid with allowances made for dilution to the volume of tions (from 0.01320 to 0.1249 mol/l), into the calorimet-
the calorimetric liquid; ∆ H and ∆ H are the molar ric vessel. For the background electrolyte, lithium nitrate
r
2
r
1
–
2–
heat effects of protonation of HSuc and Suc , respec- was used. The experimental data listed in Tables 4 and 5
tively; ∆ H is the molar heat effect of neutralization of were used for determining stepwise heats of ionization.
r
w
The calculation was performed on a 486FX PC with
a strong acid with a strong base; n is the number of
HEAT software (for the algorithm, see [25]). In a series
experiments; and ω is the weighting factor. The calcu-
–
lation was performed on a 486FX PC by using the of experiments, degrees of protonation of çí‡rt and
2
–
HEAT software (for the algorithm, see [25]). The í‡rt varied from 3 to 70% and from 30 to 98%,
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 6 2007

9
14
KOCHERGINA et al.
Table 7. Thermodynamic characteristics of the dissociation of succinic acid at different ionic strength values
I
T, K
pK
∆G, kJ/mol
∆H, kJ/mol
–∆S, J/(mol K)
–
+
H Suc = HSuc + H
2
0
298.15
4.21 ± 0.01
3.94 ± 0.05
3.96 ± 0.05
4.00 ± 0.05
4.21 ± 0.01
3.94 ± 0.05
3.96 ± 0.05
4.00 ± 0.05
4.19 ± 0.01
3.84 ± 0.05
3.83 ± 0.05
3.85 ± 0.05
4.19 ± 0.01
3.77 ± 0.05
3.75 ± 0.05
3.76 ± 0.05
24.02 ± 0.06
22.48 ± 0.30
22.60 ± 0.30
22.82 ± 0.30
24.02 ± 0.06
22.48 ± 0.30
22.60 ± 0.30
22.82 ± 0.30
24.71 ± 0.06
22.65 ± 0.30
22.59 ± 0.30
22.70 ± 0.30
25.51 ± 0.06
22.95 ± 0.30
22.83 ± 0.30
3.45 ± 0.25
4.44 ± 0.17
4.87 ± 0.17
5.09 ± 0.17
3.43 ± 0.30
4.44 ± 0.20
4.95 ± 0.20
5.33 ± 0.20
2.19 ± 0.30
3.42 ± 0.20
4.04 ± 0.20
4.49 ± 0.20
0.90 ± 0.30
2.45 ± 0.20
3.11 ± 0.20
3.89 ± 0.20
69.2 ± 0.6
60.5 ± 1.1
59.5 ± 1.1
59.5 ± 1.1
69.0 ± 0.9
60.5 ± 1.1
59.2 ± 1.1
58.7 ± 1.1
73.1 ± 0.9
62.4 ± 1.1
60.2 ± 1.1
59.1 ± 1.1
77.3 ± 0.9
64.4 ± 1.1
62.0 ± 1.1
59.7 ± 1.1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
.5
.0
.5
298.15
308.15
318.15
.5
.0
.5
.5
.0
.5
.5
.0
.5
22.89 ± 0.30
HSuc = Suc + H+
32.18 ± 0.06
29.04 ± 0.30
29.16 ± 0.30
29.50 ± 0.30
32.18 ± 0.06
29.04 ± 0.30
29.16 ± 0.30
29.50 ± 0.30
33.32 ± 0.06
29.78 ± 0.30
29.78 ± 0.30
29.96 ± 0.30
34.52 ± 0.06
30.63 ± 0.30
30.52 ± 0.30
30.63 ± 0.30
–
2–
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
298.15
298.15
308.15
318.15
5.64 ± 0.01
5.09 ± 0.05
5.11 ± 0.05
5.17 ± 0.05
5.64 ± 0.01
5.09 ± 0.05
5.11 ± 0.05
5.17 ± 0.05
5.65 ± 0.01
5.05 ± 0.05
5.05 ± 0.05
5.08 ± 0.05
5.67 ± 0.01
5.03 ± 0.05
5.01 ± 0.05
5.03 ± 0.05
0.58 ± 0.25
2.14 ± 0.17
3.20 ± 0.17
3.65 ± 0.17
0.44 ± 0.30
2.15 ± 0.20
3.10 ± 0.20
3.42 ± 0.20
–1.57 ± 0.30
0.40 ± 0.20
1.32 ± 0.20
1.60 ± 0.20
–3.07 ± 0.30
–0.77 ± 0.20
0.23 ± 0.20
0.70 ± 0.20
106.3 ± 0.6
90.2 ± 1.1
87.1 ± 1.1
86.7 ± 1.1
106.6 ± 0.6
90.2 ± 1.1
87.4 ± 1.1
87.5 ± 1.1
113.2 ± 0.9
95.3 ± 1.1
92.4 ± 1.1
92.0 ± 1.1
118.2 ± 0.9
98.7 ± 1.1
95.1 ± 1.1
94.1 ± 1.1
.5
.0
.5
.5
.0
.5
.5
.0
.5
.5
.0
.5
Note: The weighted mean values are italicized.
respectively; pH varied from 4.1 to 2.3. We also mea-
RESULTS AND DISCUSSION
fin
sured the heat effects of dilution of the nitric acid solu-
tion with an acidified background electrolyte solution.
The measured heat effect was expressed as related to
Enthalpies of stepwise dissociation of oxyacids at
zero ionic strength were determined by the equation
with a single individual parameter [18]:
1
mol of nitric acid. Calculation results are listed in
2
Table 6.
∆H – ∆Z Ψ(I) = ∆H° + bI,
(6)
Arithmetic mean ∆H was calculated from results of where ∆H and ∆H° are enthalpy changes at a finite
five to ten measurements. The confidence interval of ionic strength value and I = 0, respectively; Ψ(I) is the
mean ∆H was calculated with the Student criterion for theoretically calculated function of the ionic strength;
2
0
.95 confidence level.
∆Z is the difference of squared charges of reaction
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 6 2007

INFLUENCE OF THE TEMPERATURE ON HEAT EFFECTS OF ACID–BASE INTERACTIONS
915
∆rH, kJ/mol
centrations, a deficiency of water molecule in the solu-
tion decreases the contribution of the “freezing” of
hydration shells of ions, which decreases the absolute
value of ∆Cp.
A rise of temperature intensifies the chaotic thermal
motion of water molecules and destroys the water
structure so that water molecules are freely oriented
around ions. Therefore, at a constant ionic strength, a
rise of temperature is accompanied by a shift of ∆disS
toward more negative values. This is supported by the
data presented in Tables 3 and 6.
4
3
1
.5
.0
.5
0
4
3
2
1
–
1.5
2
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290
295
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305
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T, K
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(
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1
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(7)
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2
16
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RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 81 No. 6 2007