Vapour pressures of 1,2-dibromoethane + benzene at temperatures between 283.15 and 323.15 K

Fluid’ Phase Equilibria,

97 (1994) 147- 153

Vapour pressures of 1,2-dibromoethane + benzene at temperatures between 283.15 and 323.15 K Mariano

Gracia

*, Pascual

Perez, Jose Valero

Department0 de Quimica Orgcinica-Quimica Fisica, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain

(Received October 13, 1993; accepted in final form December 27, 1993)

Abstract

Gracia, M., Perez, P. and Valero, J., 1994. Vapour pressures of 1,Zdibromoethane between 283.15 and 323.15 K. Fluid Phase Equilibria, 97: 147-153.

+ benzene

at temperatures

Vapour pressures of 1,Zdibromoethane, benzene and 1,Zdibromoethane + benzene at 5 K intervals between 283.15 and 323.15 K were measured by a static method. Following Barker’s method, the activity coefficients and the excess molar Gibbs energies were fitted to a Redlich-Kister second degree polynomial. The derived hE value at x = 0.5 agrees with our datum for excess molar enthalpy. Keywords: Experiments;

Data; Excess functions; VLE low pressure

1. Intmduction In a previous paper (Perez et al., 1983), excess enthalpies, excess volumes and dielectric behaviour of 1,Zdibromoethane + benzene were measured. In this paper we report vapour pressures at nine temperatures between 283.15 and 323.15 K. The conformational equilibrium in 1,Zdibromoethane and estimation of parameters in group contribution models have been regarded as important factors for consideration in this work. 2. Experimental Benzene (Aldrich, purity > 99.9 mol%), and 1,Zdibromoethane were used without further purification. * Corresponding

author.

0378-3812/94/$07.00 0 1994 - Elsevier Science B.V. All rights reserved SSDZ 0378-3812(94)02466-E

(Merck, purity > 99 mol%)

148

M. Gracia et al. /Fluid Phase Equilibria 97 (1994) 147-153

The total vapour pressure measurements were performed by a static method whose experimental details are described elsewhere (Pardo et al., 1987; Gracia et al., 1992). To avoid condensation effects on the mercury meniscus, the temperature of the manometer was maintained at 325.0 K by circulating water maintained within 0.1 K. The cell containing the sample was immersed in a water bath, the temperature of which was maintained constant to within better than 10 mK using a Haake F3 instrument. Manometer readings were made with a Wild KM-305 cathetometer to +O.Ol mm. Reproducibility of the pressure measurements is estimated to be better than 15 Pa. Errors in the mole fraction are estimated to be less than 3 x 10m4. A densimeter (Anton Paar DMA 60/DMA 602) was used for density measurements on the pure 1,Zdibromoethane.

3. Results and discussion Molar volumes of the pure compounds are collected in Table 1. The virial coefficient of benzene (BBB= - 1190 cm3 mol-‘) at 325.0 K was calculated from the work of Al-Bizreh and Wormald ( 1977), and that of 1,Zdibromoethane (/I?AA= - 3442 cm3 mol-‘) from the Tsonopou10s correlation (Tsonopoulos, 1974). The virial mixed coefficient (DAB= -2121 cm3 mol-r) was calculated from Berthelot’s equation. Vapour pressures of the pure liquids were measured at nine temperatures and data for 1,Zdibromoethane were fitted to the Antoine equation: ln(p*/kPa)

= 13.03388 -

2777.47 1 (T/K) - 78.096

(1)

Table 2 includes the experimental vapour pressures of both compounds together with values obtained from the literature. For l,Zdibromoethane, vapour pressures calculated from Eq. (1) show a standard deviation of 10 Pa and a maximum deviation of + 13 Pa at 3 18.15 K. Table 3 shows our vapour pressures measurements along with the activity coefficients YAand YB,and the GE values fitted to a Redlich-Kister polynomial by Barker’s method (Barker, 1953): GE/RT=xA(l

-XA) C Aj(l

-hA)j

j=O

where XAis the mole fraction of 1,Zdibromoethane in the liquid phase. For a given composition, the sample temperature is changed and a slight variation of the true liquid mole fraction may be Table 1 Molar volumes V& (cm3 mol-I) used in Barker analysis

1,2-Dibromoethane Benzene b

a

283.15

288.15

293.15

298.15

303.15

308.15

313.15

318.15

323.15

85.17 87.80

85.65 88.30

86.13 88.90

86.62 89.40

87.11 90.00

87.62 90.50

88.13 91.10

88.64 91.70

89.15 92.30

a This work. b Timmermans (1965).

149

M. Gracia et al. 1Fluid Phase Equilibria 97 (1994) 147-153

Table 2 Vapour pressure p* (Pa) of the pure compounds

T (K)

Benzene

283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15

6060 7827 10040 12697 15928 19809 24406 29820 36193

1,2-Dibromoethane 6082 7853 10034 12697 15919 19784 24384 29819 36196

a a a a a a a a a

595 840 1120 1515 1993 2606 3369 4336 5477

b b b b b b b b b

B a a a = a a a a

580 * 1072 * 1612 = 1932 * 2649 d -

a This work. b Ambrose (1977). ’ Kalra et al. (1991). d Kalra et al. (1990). e Gmehling extrapolated from the Antoine equation. f Neckel and Volk (1958).

628 865 1176 1577 2088 2731 3534 4525 5738

= = e = = = = e =

et al. (1980); values

detected according to the variable composition of the vapour phase. Coefficients of Eq. (2) together with the standard deviations are collected in Table 4. Vapour pressure curves and excess molar Gibbs energies, at 10 K intervals, are shown in Fig. 1. All the GE values found in the literature are higher than ours. At x = 0.5, Neckel and Volk (1958) give 194, 185 and 173 J mol-’ at 283.15, 293.15 and 303.15 K, respectively. At 293.15 K, Birdi et al. (1974) give GE& = 0.5) = 161 J mol-‘. Abnormally large discrepancies are observed between our values and those by Kalra et al., at 298.15 K, GE@ = 0.5) = 250 J mol-’ (Kalra et al., 1991) and at 308.15 K, GE (x = 0.5) = 280 J mole1 (Kalra et al., 1990). However, these values give a positive temperature coefficient for the excess Gibbs energy, whereas a negative coefficient is obtained with our results. Our GE (x = 0.5) experimental values, at different temperatures, are shown in Table 5.

32.0

16.0

(aI

0.2

0.4

0.6

0.8

Fig. 1. (a) Vapour pressure P, at 5 K intervals and (b) Excess molar Gibbs energies GE, at 10 K intervals, for x1,2C,H,Br, + (1 - x)C,H,.

150

M. Gracia et al. 1 Fluid Phase Equilibria 97 (1994) 147-153

Table 3 Values of the vapour pressure P, deviations AP = P -Pa,, energies GE, for (xA I,2-C,H,Br, + x,CsH,)

activity coefficients yA and yr,, and excess molar Gibbs

AP (Pa)

YA

YB

GE (J mol-‘)

5564 5478 4830 4189 3586 3321 2877 1972 1579 807

14 7 -12 0 -5 -3 24 -19 -5 38

1.2219 1.2082 1.1346 1.0988 1.0794 1.0716 1.0570 1.0268 1.0138 1.0004

1.0048 1.0061 1.0195 1.0337 1.0475 1.0553 1.0754 1.1551 1.2242 1.4331

57 64 107 131 143 146 146 122 97 19

0.1004 0.1161 0.2424 0.3694 0.4827 0.5330 0.6219 0.7837 0.8559 0.9786

7211 7085 6269 5412 4656 4330 3732 2598 2081 1105

34 7 -4 -21 -6 12 19 -13 -14 45

1.2128 1.1989 1.1256 1.0923 1.0754 1.0686 1.0556 1.0269 1.0141 1.0004

1.0049 1.0063 1.0197 1.0330 1.0449 1.0517 1.0697 1.1456 1.2137 1.4235

57 64 104 127 139 141 142 120 96 19

293.15

0.1004 0.1162 0.2425 0.3697 0.4829 0.5332 0.6221 0.7839 0.8560 0.9786

9241 9094 8065 6959 5974 5580 4820 3356 2696 1436

30 12 9 -24 -27 18 33 -16 -14 40

1.2108 1.1969 1.1235 1.0892 1.0717 1.0650 1.0522 1.0250 1.0131 1.0004

1.0049 1.0063 1.0197 1.0334 1.0458 1.0527 1.0704 1.1422 1.2055 1.3986

58 64 105 128 138 140 140 117 93 18

298.15

0.1006 0.1162 0.2426 0.3698 0.4832 0.5336 0.6223 0.7841 0.8563 0.9786

11706 11502 10179 8862 7607 7095 6138 4310 3473 1913

53 7 -25 0 -24 15 28 -17 -17 59

1.2049 1.1919 1.1210 1.0866 1.0686 1.0617 1.0232 1.0121 1.0003

1.0046 1.0060 1.0190 1.0328 1.0457 1.0527 1.0703 1.1386 1.1975 1.3733

57 64 104 127 137 139 138 114 90 18

0.1008 0.1163 0.2427 0.3702 0.4833

14697 14432 12786 11120 9606

73 4 -31 -14 9

1.1968 1.1840 1.1143 1.0819 1.0657

1.0047 1.0060 1.0189 1.0320 1.0435

56 63 102 123 133

T(K)

XA

283.15

0.1003 0.1161 0.2423 0.3692 0.4825 0.5327 0.6217 0.7836 0.8558 0.9785

288.15

303.15

p (Pa)

1.0491

151

M. Gracia et al. I Fluid Phase Equilibria 97 (1994) 147-153 Table 3 (continued)

TW

*A

p (Pa)

AP (Pa)

YA

YE

GE (J mol-‘)

0.5340 0.6226 0.7843 0.8565 0.9787

8897 7719 5461 4409 2486

-6 28 -13 -27 74

1.0594 1.0478 1.0230 1.0120 1.0003

.0500 .0661 .1316 .1894 .3638

135 134 112 89 18

308.15

0.1011 0.1165 0.2429 0.3707 0.4838 0.5341 0.6230 0.7845 0.8568 0.9787

18268 17913 15912 13828 11956 11067 9651 6882 5566 3202

85 -25 -18 -10 12 -31 44 -3 -39 82

1.1815 1.1705 1.1101 1.0811 1.0657 1.0594 .0476 .0226 .0117 BOO3

1.0041 1.0053 1.0165 1.0282 1.0393 1.0457 .0621 1.1278 1.1851 .3546

53 59 97 119 130 132 132 111 88 17

313.15

0.1014 0.1166 0.2432 0.3713 0.4843 0.5347 0.6231 0.7849 0.8571 0.9788

22501 22069 19625 17040 14773 13713 11978 8533 6977 4054

100 -34 -6 -30 7 -19 57 -34 -16 76

.1723 .1627 1.1072 1.0784 1.0621 1.0555 1.0437 1.0201 1.0103 1.0003

1.0037 1.0047 1.0151 1.0268 1.0386 1.0453 1.0618 1.1235 1.1749 1.3219

51 57 94 116 127 129 128 106 83 16

318.15

0.1019 0.1169 0.2435 0.3722 0.4849 0.5355 0.6236 0.7854 0.8575 0.9788

27479 27022 24007 20874 18121 16896 14756 10543 8657 5138

104 3 -15 -41 -20 10 65 -47 -13 84

1.1687 1.1597 1.1053 1.0751 1.0576 1.0508 1.0391 1.0175 1.0089 1.0002

1.0035 1.0044 1.0148 1.0272 1.0398 1.0469 1.0633 1.1200 1.1650 1.2891

50 56 94 116 125 126 124 100 78 15

323.15

0.1025 0.1171 0.2440 0.3733 0.4858 0.5364 0.6243 0.7859 0.8580 0.9789

33332 32783 29191 25358 22049 20526 17950 12870 10676 6390

101 -30 3 -49 0 -2 70 -81 26 55

1.1622 1.1533 1.0989 1.0705 1.0549 1XI488 1.0381 1.0175 1.0089 1.0003

1.0036 1.0046 1.0150 1.0267 1.0381 1.0444 1.0593 1.1137 1.1583 1.2836

50 56 92 113 121 123 121 98 77 15

152

AL Gracia et al. 1 Fluid Phase Equilibria 97 (1994) 147-153

Table 4 Coefficients Aj, and standard deviations u(P) for least-squares representation by Eq. (2)

T(K)

A0

Al

A2

*

283.15 288.15 293.15 298.15 303.15 308.15 313.15 318.15 323.15

0.2453 0.2331 0.2280 0.2219 0.2123 0.2042 0.1960 0.1900 0.1814

-0.0501 - 0.0490 -0.0405 - 0.0349 -0.0343 - 0.0428 -0.0371 - 0.0263 - 0.0256

0.1016 0.1089 0.1022 0.0928 0.0961 0.0880 0.0733 0.0610 0.0664

18 23 27 32 39 41 50 55 57

(Pa)

Table 5 GE (X = 0.5); experimental values and values calculated from Eq. (4)

T W)

GE(exp.) (J mol-‘) GE (talc.) (J mol-‘)

288.15

298.15

308.15

318.15

140 142

138 137

131 131

126 126

Our experimental results show that the excess molar Gibbs energy, at x = 0.5, varies almost linearly with temperature and according to the relationship GE=HE-TSE

(3)

excess enthalpy and excess entropy, at x = 0.5, must be independent of temperature, at least in the range examined by us. GE (x = 0.5) values at different temperatures have been fitted by the least-squares method to Eq. (3), obtaining SE = 0.55 J mol-’ K-r and HE = 299 J mol-‘. Our experimental results of HE (Perez et al., 1983) at four temperatures between 288.15 and 318.15 K oscillate from 293 to 299 J mol-I, giving a remarkable agreement with the calculated value. For HE, at 293.15 K and x = 0.5, Kohler (1969) gives 301 J mol-’ whereas Mahl et al. (1976) and Spah (1989), 298.15 K and x = 0.5, give 250 J mol-‘, about 15% lower than our value. In the absence of independent values of the activity coefficients we cannot use the GibbsDuhem relation to test the thermodynamic consistency of the vapour pressure measurements. We can, however, test the consistency of the enthalpy and free energy data by integrating the Gibbs-Helmholtz equation. Assuming that HE is independent of temperature the integration gives

GE@,Td = GE@,TI) T2

Tl

In Table 5, GE (0.5, Tz) calculated values are compared with the experimental ones, taking T, = 303.15 K and using an average value for the excess enthalpy (HE(x =0.5)) = 296 J mol-‘.

M. Gracia et al. /Fluid Phase Equilibria 97 (1994) 147-153

153

At other mole fractions a similar agreement is observed, except at 318.15 K and 0.7, 0.8 and 0.9 mole fractions of 1,2-dibromoethane, where the GE calculated values are about 8 J mol-’ higher.

4. Acknowledgement The authors are grateful for financial assistance from the Universidad de Zaragoza, (Proyecto 5411/640).

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