Excess molar enthalpies at 298.15 K of (1-chloropentane + nonane or decane) and of (1-chlorohexane + nonane or decane or undecane)

M-2357 J. c‘hcm.

Thermo&zamics

1989, 21, 495-497

Excess molar enthalpies at 298.15 K of (1 -chloropentane + nonane or decane) and of (1 -chlorohexane + nonane or decane or undecane) L. NtJi%EZ.” F. MIGUELEZ,h M. I. PAZ ANDRADE

L. BARRAL.

and

Departamento de Fisica Aplicada, Facultade de Fisk, Universidade de Santiago de Compostela. Spain i Received 25 January 1989)

Excess molar enthalpies Hk, have been measured at atmospheric pressure and 298.15 K for (.YCH,(CH,),CI + (I -x)CH,(CH,),CH3 or (1 -x)CH,(CH,),CH,} and for {uCH,(CH,),CI + (1 -x)CH,(CH,),CHa or (1 -x)CH,(CH,),CH, or (1 -x)CH,(CH,)~CH,). All the mixtures have Hz > 0 and the Hz(x) curves deflect slightly towards .Y > 0.5. that is towards the more chloroalkane-rich compositions.

1. Introduction As a contribution to the study of the mixtures (a chloroalkane + an alkane),” report here the experimental excess molar enthalpies Hg for {xCH,(CH,),CI (1 - x)CH,(CH,),CH, or (1 -x)CH3(CH,),CH3] and for jxCH,(CH,),CI (1 -x)CH,(CH,),CH, or (1 -x)CH,(CH,),CH, or (I -x)CH,(CH,),CH,).

3, we + +

2. Experimental Excess molar enthalpies were determined using a standard Calvet microcalorimeter calibrated electrically, the calibration having been checked by determining, for the entire range of compositions, the excess molar enthalpies of the standard: (hexane + cyclohexane). Our results agree within 0.9 per cent with those of McGlashan and Stoekli.‘3’ The calorimetric technique has been previously described.‘4’ All the liquids used were Fluka with purity levels of 99 moles per cent or better and, since their densities and refractive indices do not differ significantly from those in the literature,‘s’ no purification was attempted. “To whom correspondence should be addressed. “Colexio Universitario de A Corufia, Universidade

0021-9614/89/050495+03

tsOZ.OO/O

de Santiago

de Compostela.

Spain

,(‘i 1989 Academic

Press Limited

496 TABLE

x

L. NUNEZ 1. Excess molar

H; J.mol~

enthalpies

Hk of (1-chloropentane + an alkane) alkane) at 298.15 K

H!i ’

x

J.mol

x

J’mol

345 357 426

0.3323 0.3895 0.4668

472 505 525

0.1594 0.2238 0.2857

291 386 451

0.3582 0.4151 0.4650

514 550 562

0.1114 0.2036 0.2473

185 296 346

0.2907 0.3589 0.4108

378 423 438

0.1359 0.2150 0.3170

222 328 407

0.3795 0.4243 0.49 12

458 463 472

0.1596 0.2285 0.2933

276 346 412

0.4070 0.4377 0.4663

494 454 502

0.4898 0.5472 0.5952

565 561 550

xCH,(CH,),CI+(l

Hk

J’mol

1

X

HL

J,mol

’

x

J.mol

’

0.6882 0.6897 0.7331

457 448 411

0.7762 0.8103 0.8646

371 331 248

0.8966

191

0.6135 0.6618 0.7592

536 503 418

0.8252 0.8510 0.8615

339 330 276

0.8800 0.9129 0.9330

246 177 148

0.7526 0.7889 0.8326

332 293 248

0.8838 0.9 162

181 130

375 325 267

0.8441 0.9014 0.9308

254 173 123

436 388 347

0.8487 0.8500 0.8988

267 263 189

0.9966

147

-x)CH,(CH2),CH3 450 450 434

xCH,(CH,),Cl

0.6235 0.6589 0.7193

417 408 355

+(l -.Y)CH~(CH,)&H, 464 462 416

uCH,(CH,),CI 0.5125 0.5649 0.6100

x

+(I -x)CH,(CH,),CH,

0.5187 0.5400 0.5687

0.5900 0.5927 0.6753

’

+ an

1 -x)CH,(CH,),CH, 529 528 509

.xCH,(CH,),CI

0.4713 0.5020 0.5881

and of (I-chlorohexane

H;

H!i ’

.xCH,(CH,),Cl+( 0.2024 0.2081 0.2655

ET AL.

0.7277 0.7844 0.8332 +( 1 -x)CH,(CH,)&H,

510 500 490

0.6892 0.7463 0.7822

3. Results and discussion Table 1 summarizes the HE(x) results. The values of Hk were curve-fitted using the equation: H~J(J~molk’)

= x(1-x)

f

The coefficients A, were calculated by the least-squares determined by applying an F-test for the significance coefficients are listed in table 2 together with standard enthalpies are positive. Examination of the excess molar

TABLE

2. Coefficients

A, of

equation

method, their number being of successive terms. These deviations s. All the excess enthalpies shows, for a given

(1) and standard

A0 xCH,(CH,),CI+(l +(l xCH,(CH~)~C~+(~ +(l +(I

-x)CH,(CH2),CH3 -x)CH,(CH,),CH, -x)CH,(CH&CH, -x)CH,(CHz)sCH, -x)CH,(CH&CH,

(1)

A,(1 -2x)“.

2126.1 2253.3 1805.2 1908.8 2029.0

deviations

s

A,

s

-31.3 78.2 -67.3

4.6 4.5 3.0 4.0 4.3

54.5

Hi

of (I CHLOROPENTANE

against FIGURE I. H:.,,, bCH,V.X,),Cl + (1 -.KHzn+z, & 0, literature values.

OR

I CHLOROHEXANE

+ ALKANE)

497

N (number of carbons) for (xCH,(CH,),CI + (I px)C.HZn+2) and for t at 298.15 K. A. CH,(CH,),CI: 0. CH,(CH2),CI: A, n . our values:

chloroalkane, that Hti, increases linearly with the length of the alkane chain. The H:(x) curves deflect slightly towards x > 0.5, that is towards the more chloroalkanerich compositions. In figure 1 the maximum excess molar enthalpies Hk.,,, are plotted against the number N of carbon atoms in the alkane for chloropentane and for chlorohexane. The excess molar enthalpies increase systematically with N. The maximum values of the excess molar enthalpy increase both for chloropentane and for chlorohexane by about 30 J. mol- ’ with each integral value of N. In the two chloroalkanes studied the excess molar enthalpies decrease with the number of carbon atoms in the chloroalkane. The maximum values Hz, max show a regular decrease of about 80 J. mol- ’ from chloropentane to chlorohexane mixtures. REFERENCES I. Paz-Andrade. M. 1.; Bravo, R.; Garcia. M.: 51. 2. Handa, Y. P.; Knpbler, C. M.: Scott. R.L. 3. McGlashan, M. L.; Stoeckli, H. F. J. Chem. 4. Paz-Andrade. M. I.; Hernandez, C.: Nuiiez, 5. Riddick, J. A.: Burger, W. B. Technique.7 of York. 1970.

Grolier.

J. P. E.: Kehiaian.

J. Chem. Thermodynumicv Thermodynamics 1969, 1, L.: Jimtnez. E. J. fhim. Chemistry. Third edition,

H. V. J. C’him. Ph~.v. 1979, 76. 1977, 9. 451. 589. Phys, 1972, 7. 1 131. Vol 2. Wiley-Interscience:

Neu