Thermodynamic Properties of Inorganic Salts in Nonaqeous Solvents

Chemical Faculty, Gdansk University of Technology, 80-952 Gdansk, Poland. The densities of divalent transition-metal bromides and chlorides in acetoni...
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J. Chem. Eng. Data 2007, 52, 2105-2109

2105

Thermodynamic Properties of Inorganic Salts in Nonaqeous Solvents. IV. Apparent Molar Volumes and Compressibilities of Divalent Transition-Metal Bromides and Chlorides in Acetonitrile Joanna Krakowiak,* Dorota Warmin´ ska, and Wacław Grzybkowski Chemical Faculty, Gdan´sk University of Technology, 80-952 Gdan´sk, Poland

The densities of divalent transition-metal bromides and chlorides in acetonitrile at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and sound velocities at 298.15 K have been measured. From these data, apparent molar volumes VΦ at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and the apparent molar isentropic compressibility KS,Φ at T ) 298.15 K of transition-metal bromides and chloride in acetonitrile have been determined.

3[ZnCl2(CH3CN)2] + 2CH3CN )

Introduction This study is a part of an investigation of the volumetric properties of nonaqueous solutions.1-3 Divalent first-row transition-metal cations are known to form well-defined coordination forms in acetonitrile (AN) and to exist as M(AN)62+ solvates in the absence of coordinating anions.4 It has been established that the volumetric properties of such solvates exhibit variation, which can be interpreted in terms of ligand field theory.5,6 Unlike perchlorates, the divalent transition-metal bromides and chlorides dissolved in acetonitrile exhibit a variety of electrolytic behaviors due to a more complicated system of complex formation equilibria. Acetonitrile solutions of CoBr2 have been investigated spectrophotometrically,7-9 and these studies have yielded good evidence for the existence of two pseudotetrahedral species, [CoBr2(CH3CN)2] and [CoBr3(CH3CN)]-. In the case of MnBr2 acetonitrile solutions, ions form the [Mn(CH3CN)6]2+‚2[MnBr3 (CH3CN)]- (disproportionation) cation and anion complex. The most characteristic feature of the acetonitrile solutions of ZnBr2 is the existence of electrically neutral tetrahedral complexes of ZnBr2(CH3CN)2. The dissolution of anhydrous cobalt(II) chloride in acetonitrile is accompanied by two reactions10

[Zn(CH3CN)6]2+ + 2[ZnCl3(CH3CN)]was found to be responsible for the electrical conductivity of ZnCl2 in acetonitrile. However, the extreme stability of tetrahedral complexes of zinc(II) appears to be amenable for the existence of the neutral [ZnCl2(CH3CN)2] complexes in solution in the presence of a small amount of the [Zn(CH3CN)6]2+ and [ZnCl3(CH3CN)]- complex electrolyte. The apparent molar volume VΦ of a solute is defined as the difference between the volume of the solution and the volume of the pure solvent per mole of solute and is given by VΦ ) (V - n0V00)/nS

where V denotes the volume of the solution; n0 and nS are the number of moles of the solvent and salt, respectively; and V00 is the molar volume of pure solvent. The adiabatic compressibility, defined by the thermodynamic relation κS ) -(1/V)(∂V/∂P)S

3CoCl2 + 8CH3CN ) [Co(CH3CN)6]2+ + 2[CoCl3(CH3CN)]Consequently, in the solution, the following equilibrium establishes (with an equilibrium constant of ca. 5‚10-3) 3[CoCl2(CH3CN)2] + 2CH3CN ) [Co(CH3CN)6]2+ + 2[CoCl3(CH3CN)]Coordination properties of cobalt(II) and zinc(II) are known to be rather similar, and the equilibrium * Corresponding author. E-mail: [email protected].

(2)

where V is volume, P is pressure, and S is entropy, is related to the density d and the sound velocity u, by Laplace’s equation

CoCl2 + 2CH3CN ) [CoCl2(CH3CN)2] and

(1)

κS ) 1/(u2d)

(3)

providing the link between thermodynamics and acoustics. In this paper, experimental data at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K for density of MnBr2, CoBr2, ZnBr2, CoCl2, and ZnCl2 and data at 298.15 K for sound velocity of studied bromides and cobalt(II) chloride in acetonitrile solutions are reported. The apparent molar volume, VΦ, adiabatic compressibility, κS, and apparent molar adiabatic compressibility, KS,Φ, are obtained from the measured properties.

Experimental Section The anhydrous CoBr2, MnBr2, ZnBr2, CoCl2, and ZnCl2 were prepared from the corresponding hydrates by drying under a vacuum initially at 353 K and then at 423 K. These were recrystallized at least twice from anhydrous acetonitrile. The stock solutions were obtained by dissolution of the solids in

10.1021/je7001946 CCC: $37.00 © 2007 American Chemical Society Published on Web 09/14/2007

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Journal of Chemical and Engineering Data, Vol. 52, No. 6, 2007

Table 1. Densities of the Pure Acetonitrile, d0, and the Solutions, d, of the Metal Halides in Acetonitrile at Different Temperatures d/kg‚m-3 /mol‚kg-1

mS

288.15 K

293.15 K

298.15 K

303.15 K

308.15 K

313.15 K

323.15 K

777.408 778.907 780.415 781.978 783.537 784.953 786.518 789.765 792.776 795.916 797.634 799.110 802.149 771.097

771.942 773.433 774.941 776.494 778.054 779.461 781.030 784.269 787.272 790.407 792.128 793.589 796.622 765.640

766.441 767.926 769.432 770.984 772.539 773.940 775.513 778744 781.741 784.868 786.584 788.041 791.065 760.148

755.330 756.805 758.311 759.855 761.403 762.804 764.368 767.585 770.567 773.687 775.396 776.847 779.856 749.055

781.218 783.966 786.563 789.080 791.742 794.089 796.713 801.964 807.083 812.642 814.557 816.995 822.494 771.112

775.720 778.458 781.049 783.570 786.222 788.550 791.168 796.411 801.513 807.057 808.967 811.404 816.889 765.653

770.192 772.920 775.500 778.020 780.656 782.985 785.595 790.822 795.917 801.450 803.340 805.778 811.253 760.164

759.026 761.738 764.302 766.801 769.421 771.734 774.335 779.533 784.593 790.088 791.988 794.405 799.854 749.073

775.922 777.179 778.202 779.559 780.651 781.876 783.143 785.546 787.860 790.202 791. 221 792.539 771.106

770.453 771.701 772.724 774.080 775.170 776.393 777.651 780.047 782.357 784.687 785.702 787.024 765.650

764.950 766.197 767.215 768.567 769.655 770.874 772.126 774.520 776.822 779.149 780.162 781.476 760.159

753.836 755.075 756.090 757.437 758.516 759.730 760.980 763.359 765.649 767.969 768.971 770.273 749.070

779.137 781.889 784.571 787.274 790.011 792.763 795.467 798.109 771.090

773.654 776.401 779.078 781.773 784.510 787.256 789.954 792.590 765.631

768.139 770.881 773.545 776.240 778.973 781.714 784.407 787.039 760.142

756.997 759.736 762.939 765.073 767.796 770.528 773.206 775.843 749.056

775.724 776.886 777.790 778.553 780.640 782.455 784.317 786.115 788.091 790.032 771.095

770.266 771.431 772.330 773.096 775.184 777.003 778.858 780.661 782.635 784.575 765.637

764.781 765.940 766.841 767.607 769.697 771.516 773.372 775.165 777.148 779.089 760.151

753.694 754.859 755.760 756.526 758.618 760.435 762.295 764.103 766.072 768.014 749.071

MnBr2 0.04150 0.05130 0.06115 0.07131 0.08138 0.09054 0.1006 0.1214 0.1406 0.1603 0.1712 0.1804 0.1995 AN

793.652 795.156 796.676 798.243 799.819 801.238 802.824 806.091 809.125 812.287 814.024 815.501 818.585 787.299

788.260 789.764 791.280 792.850 794.414 795.840 797.413 800.671 803.696 806.853 808.580 810.054 813.117 781.923

782.850 784.353 785.862 787.428 788.989 790.408 791.982 795.230 798.249 801.398 803.121 804.590 807.642 776.525

0.06384 0.08092 0.09698 0.1125 0.1286 0.1428 0.1587 0.1900 0.2204 0.2527 0.2636 0.2777 0.3089 AN

797.529 800.300 802.926 805.465 808.142 810.505 813.161 818.466 823.615 829.214 831.140 833.591 839.134 787.315

792.118 794.880 797.495 800.033 802.700 805.061 807.703 812.988 818.130 823.715 825.637 828.085 833.612 781.939

786.677 789.432 792.044 794.565 797.232 799.583 802.224 807.489 812.623 818.194 820.113 822.557 828.072 776.538

0.03209 0.04040 0.04717 0.05609 0.06324 0.07124 0.07952 0.09524 0.1099 0.1252 0.1317 0.1402 AN

792.171 793.435 794.467 795.839 796.938 798.167 799.446 801.876 804.162 806.567 807.593 808.922 787.313

786.781 788.040 789.072 790.436 791.534 792.766 794.033 796.466 798.743 801.138 802.157 803.487 781.935

781.365 782.622 783.650 785.044 786.108 787.332 788.597 791.020 793.295 795.677 796.698 798.026 776.535

0.08764 0.1171 0.1460 0.1743 0.2031 0.2318 0.2600 0.2873 AN

795.418 798.185 800.890 803.599 806.356 809.121 811.836 814.493 787.297

790.014 792.779 795.475 798.184 800.934 803.697 806.407 809.058 781.919

784.590 787.348 790.038 792.742 795.487 798.244 800.953 803.595 776.518

0.05257 0.06571 0.07576 0.08438 0.1077 0.1280 0.1487 0.1684 0.1902 0.2114 AN

791.935 793.095 794.000 794.764 796.850 798.676 800.536 802.335 804.302 806.244 787.303

786.551 787.712 788.618 789.380 791.469 793.289 795.155 796.955 798.922 800.862 781.922

781.150 782.313 783.217 783.985 786.068 787.887 789.746 791.541 793.519 795.456 776.522

CoBr2

ZnBr2

CoCl2

ZnCl2

anhydrous solvent. The stock solutions of the metal halides were prepared and analyzed for the respective metals by standard EDTA titration. At least ten determinations were performed in each case, and the relative standard deviations were smaller than

( 0.1 %. Solutions for the density measurements were prepared by weighed dilutions of the corresponding stock solutions, and the vacuum corrections were taken into account. All the preparations and manipulations involving anhydrous materials

Journal of Chemical and Engineering Data, Vol. 52, No. 6, 2007 2107 Table 2. Parameters of Equation 5 for Metal Bromides and Chlorides in Acetonitrile at Different Temperatures

salt

MnBr2

CoBr2

Figure 1. Apparent molar volumes, VΦ, against the square root of molarity, c, in acetonitrile solutions at 298.15 K of: [, MnBr2; 2, CoBr2; 9, ZnBr2; 4, CoCl2; and 0, ZnCl2 .

ZnBr2

CoCl2

ZnCl2

Figure 2. Values of the coefficient of eq 5, A∞Φ, against temperature from T ) (288.15 to 323.15) K in acetonitrile solutions for: [, MnBr2; 2, CoBr2; 9, ZnBr2; 4, CoCl2; and 0, ZnCl2.

were performed in dryboxes. Acetonitrile (Aldrich, H2O < 5‚10-3 %) was dried with 4A molecular sieves. The densities of the solutions were measured using an Anton Paar DMA 5000 densimeter with a precision of 1.0 ·10-3 kg‚m-3 and uncertainties of 5.0 ·10-3 kg‚m-3 for a single measurement. The instrument was equipped with the Peltier-type thermostating unit, and the temperature was kept constant at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K with uncertainties ( 0.001 K. The uncertainties of the density measurements and purity of the solvents were verified by measurements of their densities at 298.15 K. The density value of (776.532 ( 0.007) kg‚m-3 for acetonitrile was found, whereas the literature values11,12 vary from 775.9 kg‚m-3 to 776.85 kg‚m-3. The sound velocities were measured using the sound analyzer OPTIME 1.0 from Optel (Poland) with a precision of 0.05 m‚s-1 by measuring the time it takes for a pulse of ultrasound to travel from one transducer to another (pitch-catch) or to return to the same transducer (pulse-echo). The cell was thermostated at (298.15 ( 0.005) K and calibrated with double distilled water, and the value of 1496.69 m‚s-1 for the sound velocity in pure water has been used.13 A value of 1278.28 m‚s-1 obtained for sound velocity in pure acetonitrile compares reasonably well with literature values,14 1277.03 m‚s-1 and 1280.80 m‚s-1.

Results and Discussion The density data obtained for the solutions of the transitionmetal bromides and chlorides are given in Table 1. The

288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K

A∞Φ‚106

AΦ‚106

σ ·106

m3‚mol-1

(m9‚mol-3)1/2

m3‚mol-1

26.8 ( 0.43 25.6 ( 0.29 24.4 ( 0.35 23.3 ( 0.33 22.1 ( 0.44 20.7 ( 0.52 17.8 ( 0.60 22.3 ( 0.20 21.7 ( 0.27 21.1 ( 0.32 20.4 ( 0.32 19.8 ( 0.42 19.2 ( 0.38 17.7 ( 0.40 42.7 ( 0.36 42.0 ( 0.29 41.4 ( 0.35 40.6 ( 0.42 39.8 ( 0.56 38.8 ( 0.46 36.9 ( 0.56 16.3 ( 0.35 16.0 ( 0.31 15.5 ( 0.30 15.15 ( 0.25 14.7 ( 0.31 14.3 ( 0.25 13.4 ( 0.27 31.6 ( 0.36 31.0 ( 0.35 30.1 ( 0.35 29.3 ( 0.30 28.4 ( 0.30 27.6 ( 0.29 26.0 ( 0.41

0.21 ( 0.035 0.24 ( 0.022 0.27 ( 0.031 0.27 ( 0.029 0.29 ( 0.037 0.31 ( 0.045 0.36 ( 0.051 0.10 ( 0.016 0.09 ( 0.018 0.07 ( 0.021 0.06 ( 0.025 0.05 ( 0.027 0.02 ( 0.028 0.00 ( 0.031 0.11 ( 0.035 0.12 ( 0.030 0.11 ( 0.034 0.12 ( 0.041 0.12 ( 0.056 0.13 ( 0.052 0.14 ( 0.056 0.06 ( 0.028 0.05 ( 0.026 0.04 ( 0.026 0.025 ( 0.021 0.01 ( 0.024 0.00 ( 0.019 -0.03 ( 0.026 0.02 ( 0.027 0.01 ( 0.032 0.03 ( 0.031 0.03 ( 0.030 0.03 ( 0.030 0.03 ( 0.029 0.00 ( 0.043

0.12 0.072 0.088 0.080 0.12 0.13 0.26 0.051 0.065 0.076 0.082 0.10 0.11 0.11 0.081 0.068 0.084 0.095 0.14 0.12 0.14 0.069 0.062 0.062 0.054 0.060 0.048 0.058 0.080 0.086 0.090 0.079 0.073 0.074 0.11

corresponding values of the apparent molar volumes, VΦ/m3‚ mol-1, were calculated using the equation VΦ ) M/d0 - (d - d0)/(mSdd0)

(4)

where mS/mol‚kg-1 denotes the number of moles of the solute per kilogram of the solution (molonity (mS), mS‚d is equal to the molarity, c/mol‚m-3); d/kg‚m-3 and d0/kg‚m-3 are the densities of the solution and the solvent, respectively; and M/kg‚ mol-1 is the molar mass of the solute. Figure 1 shows the apparent molar volume plotted against the square root of concentration for MnBr2, CoBr2, ZnBr2, CoCl2, and ZnCl2 in acetonitrile solution at 298.15 K. As seen, the plots are linear and the equation VΦ ) A∞Φ + ASΦ‚c1/2

(5)

is valid. The same finding, i.e., linearity of the VΦ vs c1/2 plots, is observed for all bromides and chlorides irrespective of temperature. Moreover, the values of the apparent molar volume for ZnBr2 are much higher than for other studied bromides, due to the ability of the Zn(II) ion to form the tetrahedral and neutral complexes, caused by the smallest effect of electrostriction in the solution of ZnBr2. The respective coefficients of eq 5, A∞Φ and ASΦ, obtained at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K for the studied solutions of the metal bromides and chlorides are listed in Table 2. Inspection of the data listed in Table 2 reveals that an increase in temperature causes a distinct decrease in the values of coefficients of eq 5, A∞Φ, of the metal bromides and chlorides.

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Journal of Chemical and Engineering Data, Vol. 52, No. 6, 2007

Table 3. Parameters of Equation 6 for Metal Bromides and Chlorides in Acetonitrile 106‚AT(A∞Φ)

107‚BT

109‚CT

106‚σ

salt

m3‚mol-1

m3‚mol-1‚K-1

m3‚mol-1‚K-2

m3‚mol-1

MnBr2 CoBr2 ZnBr2 CoClr2 ZnCl2

24.4 ( 0.35 21.1 ( 0.32 41.4 ( 0.35 15.15 ( 0.25 30.1 ( 0.35

-2.37 ( 0.070 -1.28 ( 0.062 -1.46 ( 0.041 -0.08 ( 0.013 -0.165 ( 0.011

-0.9 ( 0.36 -0.3 ( 0.33 -1.4 ( 0.22 -

0.12 0.11 0.064 0.068 0.081

Table 4. Ultrasonic Velocity, u (1278.28 m‚s-1 for Pure Acetonitrile), Adiabatic Compressibility, Ks (7.881‚10-10 m2‚N-1 for Pure Acetonitrile), and Apparent Molar Compressibility, KS,Φ, for Metal Bromides and Chloride in Acetonitrile Solutions at 298.15 K

salt

MnBr2

CoBr2

ZnBr2

CoCl2

mS

u

1010‚κS

1013‚KS,Φ

mol‚kg-1

m‚s-1

m2‚N-1

m5‚N-1‚mol-1

0.06115 0.08138 0.1006 0.1406 0.1712 0.1995 0.09698 0.1286 0.1587 0.1900 0.2204 0.2636 0.3089 0.02964 0.04717 0.06324 0.07952 0.1099 0.1317 0.1554 0.08764 0.1171 0.1460 0.1743 0.2031 0.2318 0.2600 0.2873

1277.23 1276.92 1276.65 1276.11 1275.69 1275.31 1277.02 1276.04 1275.30 1274.64 1273.90 1273.20 1272.10 1277.07 1276.38 1275.72 1275.06 1273.60 1272.55 1271.25 1279.85 1280.49 1281.10 1281.80 1282.50 1283.23 1283.95 1284.75

7.800 7.773 7.747 7.693 7.651 7.613 7.809 7.754 7.712 7.672 7.631 7.591 7.535 7.851 7.833 7.816 7.800 7.771 7.751 7.730 7.781 7.746 7.712 7.678 7.643 7.608 7.574 7.539

-1.474 -1.472 -1.471 -1.463 -1.455 -1.446 -1.491 -1.484 -1.477 -1.467 -1.457 -1.443 -1.426 -9.813 -9.783 -9.740 -9.662 -9.359 -9.128 -8.876 -1.331 -1.340 -1.345 -1.348 -1.349 -1.352 -1.351 -1.353

Figure 3. Apparent molar compressibility, KS,Φ, against the square root of molarity, c, in acetonitrile solutions at 298.15 K of: [, MnBr2; 2, CoBr2; 9, ZnBr2; and 4, CoCl2. Table 5. Parameters of Equation 8 and the Mean Deviations for Metal Bromides and Cobalt(II) Chloride in Acetonitrile Solutions at 298.15 K 1013‚A∞K

(6)

The coefficients of eq 6 are listed in Table 3 along with the respective values of the residual variance, and in the case of the coefficients of chlorides, only AT and BT are presented, due to the linear correlation. It is evident that the first of the coefficients in eq 6 is identical to A∞Φ at 298.15 K. The observed changes are related to the fact that the structure of the solvent is weakened by an elevation of temperature, making an electrostriction effect higher. The experimental data for the sound velocity obtained at 298.15 K are presented in Table 4. The apparent molar isentropic compressibility, KS,Φ/m5‚(mol‚N)-1, for the metal bromides and cobalt(II) chloride in acetonitrile solution were calculated according to KS,Φ ) (κSd0 - κS,0d)/(mSdd0) + M‚κS/d

salt

m5‚N-1‚mol-1

MnBr2 CoBr2 ZnBr2 CoCl2

-1.44 ( 0.030 -1.47 ( 0.022 -0.90 ( 0.035 -1.24 ( 0.027

1017‚A2K

1016‚σ

(m13‚N-2‚mol-3)1/2 m8‚N-1‚mol-2 m5‚N-1‚mol-1 -0.11 ( 0.53 -0.8 ( 0.43 -3.1 ( 0.91 -1.5 ( 0.42

8 ( 2.7 8 ( 4.3 29 ( 6.0 5 ( 1.9

0.65 1.6 2.1 0.85

Table 6. Parameters of Equation 9 for the Speed of Sound (and the Mean Deviations) for the Metal Bromides and Cobalt(II) Chloride in Acetonitrile Solutions at 298.15 K

This effect is presented in Figure 2 as the function A∞Φ ) f(T). The plots are linear for chlorides and not linear for bromides, where the best fit is obtained using the equation A∞Φ ) AT + BT(T/K - 298.15) + CT(T/K - 298.15)2

1015‚A1K

(7)

where M/kg‚mol-1 is the molecular mass of the salt; mS/mol‚ kg-1 denotes the number of moles of the solute per kilogram of the solution (molonity); and d/kg‚m-3 and d0/kg‚m-3 are the densities of the solution and the solvent, respectively. The terms

102‚A2

103‚A3

σ

salt

(m5‚s-2‚mol-1)1/2

m4‚s-1‚mol-1

m‚s-1

MnBr2 CoBr2 ZnBr2 CoCl2

-5.65 ( 0.57 -1.0 ( 0.94 7 ( 5.6 -10.5 ( 2.6

-14.0 ( 0.53 -27.8 ( 0.70 -62 ( 5.9 35 ( 2.3

0.0088 0.025 0.095 0.056

κS/m2‚N-1 and κS,0/m2‚N-1 in eq 7 refer to the adiabatic compressibility of the solution and the solvent, respectively, calculated using eq 3. The obtained values of κS and KS,Φ are shown in Table 4. Inspection of the presented data shows that an increase in the concentration of the salt causes an increase in the apparent molar isentropic compressibility of the bromide solution and a decrease in the apparent molar isentropic compressibility of the chloride solution, as can be observed in Figure 3, and the equation KS,Φ ) A∞K + AK1c1/2 + AK2c

(8)

satisfactorily describes the concentration dependence. The coefficients (A∞K , A1K, and A2K) of eq 8, their standard deviations, and the respective values of the residual variance, σ, are given in Table 5. The negative values of KS,Φ are an indication of the more close-packed structure of the studied solutions than those of the pure solvent. The concentration dependences of the speed of sound, the density, and the adiabatic compressibility of solution can be represented by polynomials using the molar concentration c/mol‚ m-3 y ) A1 + A2c1/2 + A3c

(9)

Journal of Chemical and Engineering Data, Vol. 52, No. 6, 2007 2109 Table 7. Parameters of Equation 9 for the Density (and the Mean Deviations) for the Metal Bromides and Chlorides in Acetonitrile Solutions at 298.15 K A2‚102

d0 salt

MnBr2

CoBr2

ZnBr2

CoCl2

ZnCl2

kg‚m 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K 288.15 K 293.15 K 298.15 K 303.15 K 308.15 K 313.15 K 323.15 K

-3

A3‚103

σ

kg‚mol-1

kg‚m-3

190.6 ( 0.37 191.2 ( 0.55 191.9 ( 0.56 192.8 ( 0.56 193.6 ( 0.66 194.5 ( 0.70 196.4 ( 0.75 199.2 ( 0.40 200.0 ( 0.39 201.0 ( 0.39 201.8 ( 0.40 202.7 ( 0.42 203.6 ( 0.36 205.5 ( 0.41 190.0 ( 0.35 190.8 ( 0.25 191.3 ( 0.74 192.5 ( 0.91 193.2 ( 0.96 194.0 ( 0.97 196 ( 1.2 115.9 ( 0.37 116.6 ( 0.46 117.2 ( 0.46 118.0 ( 0.50 118.5 ( 0.51 119.2 ( 0.58 118 ( 7.6 111.0 ( 0.26 111.8 ( 0.33 112.4 ( 0.25 113.2 ( 0.24 114.1 ( 0.33 114.8 ( 0.24 116.6 ( 0.37

0.012 0.016 0.018 0.018 0.019 0.022 0.023 0.020 0.019 0.018 0.019 0.019 0.016 0.018 0.0065 0.0064 0.015 0.019 0.020 0.019 0.020 0.0097 0.013 0.014 0.014 0.014 0.016 0.21 0.0065 0.0082 0.0065 0.0063 0.0074 0.0058 0.0091

(kg ‚m ‚mol )

787.299 781.923 776.525 771.097 765.640 760.148 749.055 787.315 781.939 776.525 771.112 765.653 760.164 749.073 787.313 781.935 776.535 771.106 765.650 760.159 749.070 787.297 781.919 776.528 771.090 765.631 760.142 749.056 787.297 781.919 776.528 771.090 765.631 760.142 749.056

2

-3

-1 1/2

1.4 ( 0.43 1.6 ( 0.57 1.8 ( 0.60 1.8 ( 0.57 1.9 ( 0.66 2.0 ( 0.71 2.2 ( 0.81 1.2 ( 0.57 1.0 ( 0.52 0.8 ( 0.45 0.7 ( 0.53 0.6 ( 0.51 0.35 ( 0.43 0.1 ( 0.50 0.6 ( 0.28 0.65 ( 0.28 0.8 ( 0.68 0.6 ( 0.78 0.6 ( 0.86 0.7 ( 0.74 0.7 ( 0.87 0.5 ( 0.44 0.3 ( 0.60 0.2 ( 0.60 -0.4 ( 0.65 -0.1 ( 0.65 -0.3 ( 0.75 3 ( 9.6 0.2 ( 0.28 0.2 ( 0.35 0.3 ( 0.28 0.25 ( 0.25 0.0 ( 0.25 0.3 ( 0.27 0.15 ( 0.37

Table 8. Parameters of Equation 9 for the Adiabatic Compressibility (and the Mean Deviations) for the Metal Bromides and Cobalt(II) Chloride in Acetonitrile Solutions at 298.15 K 1014‚A2

1014‚A3

1013‚σ

salt

(m7‚N-2‚mol-1)1/2

m5‚N-1‚mol-1

m2‚N-1

MnBr2 CoBr2 ZnBr2 Col2C

-2.9 ( 0.28 -14 ( 6.8 -12 ( 8.2 4.5 ( 0.78

-16.4 ( 0.29 -15.0 ( 0.57 -11.2 ( 0.88 -15.09 ( 0.060

0.4 1.8 1.4 0.17

where y denotes the speed of sound in the solution, u (then A1 is the speed of sound in the pure solvent independently measured, A1 ) u0); or the density of the solution, d (then A1 is the density of the pure solvent independently measured, A1 ) d0); or the adiabatic compressibility, κS (then A1 is the adiabatic compressibility of the pure solvent independently calculated, A1 ) κS,0). The coefficients of the polynomials, their standard deviations, and the respective values of the residual variance, σ, are given

in Tables 6, 7, and 8. The different acoustic properties of the studied solutions are observed. The presence of the salt causes a decrease in the sound velocity for the metal bromides. The opposite effect is observed for cobalt(II) chloride. The difference is obviously related to the changes in solvent structure induced by the electrolytes. The studied salts exhibit different electrolytic behavior and exist as the complex electrolytes or electrically neutral species. Thus, their influence on compressibility and sound velocity is different.

Literature Cited (1) Warmin´ska, D.; Krakowiak, J.; Grzybkowski, W. Thermodynamic Properties of Inorganic Salts in Nonaqueous Solvents. I. Apparent Molar Volumes and Compressibilities of Divalent Transition-Metal Perchlorates in N,N-Dimethylformamide. J. Chem. Eng. Data 2005, 50, 221-225. (2) Krakowiak, J.; Warmin´ska, D.; Grzybkowski, W. Thermodynamic Properties of Inorganic Salts in Nonaqueous Solvents. II. Apparent Molar Volumes and Compressibilities of Divalent Transition-Metal Perchlorates in Acetonitrile. J. Chem. Eng. Data 2005, 50, 832-837. (3) Warmin´ska, D.; Krakowiak, J.; Grzybkowski, W. Thermodynamic Properties of Inorganic Salts in Nonaqueous Solvents. III. Apparent Molar Volumes and Compressibilities of Divalent Transition-Metal Chlorides in N,N-Dimethylformamide. J. Chem. Eng. Data, 52, 20992104. (4) Libus´, W.; Chachulski, B.; Grzybkowski, W.; Pilarczyk, M.; Puchalska, D. Mobilities of Complex Forming Cations in Non-Aqueos Donor Solvents. J. Solution Chem. 1981, 10, 631-648. (5) Grzybkowski, W. Variation in Stability of Monohalide Complexes and Some Properties of the Solvated Cations within the Mn2+-Zn2+ Series. Polyhedron 1990, 18, 2257-2261. (6) Krakowiak, J.; Strzelecki, H.; Grzybkowski, W. Solvation and Partial Molar Volumes of Some Transition Metal Cations in N,N-dimethylacetamide. Triethylphosphate and Acetonitrile. J. Mol. Liq. 2004, 112, 171-178. (7) Janz, G. J.; Marcinkowsky, A. E.; Venkatasetty, H. V. Cobalt(II) Halides as Electrolytes in Acetonitrile. Electrochim. Acta 1963, 8, 867-875. (8) Setili, L.; Furlani, C. Formation Equilibria of Pseudotetrahedral Co(II) Halogeno complexes in Acetonitrile. J. Inorg. Nucl. Chem. 1970, 32, 1997-2008. (9) Libus´, W.; Grzybkowski, W. Spectrophotometric study on coordination states of cobaltous bromide in acetonitrile solution. Bull. Acad. Pol. Sci. Ser. Sci. Chim. 1970, 18, 501-511 (10) Libus´, W. On the Formation of Tetrahedral Cobalt(II) Complexes in Solutions. V. Chloro complexes in Acetonitrile Solutions. Rocz. Chem. 1962, 36, 999-1010. (11) Moumouzias, G.; Panopoulos, D. K.; Ritzoulis, G. Excess Properties of the Binary Liquid System Propylene Carbonate + Acetonitrile. J. Chem. Eng. Data 1991, 36, 20-23 (12) Gill, D. S.; Singh, P.; Singh, J.; Singh, P.; Senanayake, G.; Hefter, G. Ultrasonic Velocity, Conductivity, Viscosity and Calorimetric studies of copper(I) and Sodium Perchlorates in Cyanobenzene, Pyridine and Cyanomethane. J. Chem. Soc., Faraday Trans. 1995, 90, 2789-2795. (13) Del Grosso, V. A.; Mader, C. W. Speed of Sound in Pure Water. J. Acoust. Soc. Am. 1972, 52, 1442-1446. (14) Davidson, I.; Perron, G.; Desnoyers, J. E. Isentropic Compressibilities of Electrolytes in Acetonitrile at 25 °C. Can. J. Chem. 1981, 59, 22122217. Received for review April 12, 2007. Accepted July 21, 2007. Support from the State Committee for Scientific Research (KBN) within the grant 7 T09A 016 021 is acknowledged.

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