Excess enthalpies of (acetone + water) at 278.15, 288.15, 298.15, 308.15, 318.15, and 323.15 K

8/12/2019 Excess enthalpies of (acetone + water) at 278.15, 288.15, 298.15, 308.15, 318.15, and 323.15 K

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802 H.T.FRENCHInitially, to remove the last traces of water, the distilled acetone was stored overLinde molecular sieve 3A. This proved to be disastrous; the liquid treated in this way

had a significantly higher density and produced different i.r. spectra. Evidently theacetone had undergone a reaction, probably a dimerization to 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol) or its dehydration product 4-methyl-3-pentene-2-one (mesityl oxide) in the presence of the molecular sieve. Thus acetone cannot bedried by simply passing it through molecular sieve without further treatment.The density of acetone was measured by pyknometry in a thermostatted bathcontrolled to f0.002 K. Each determination was done in triplicate. with the usualprocedures for buoyancy correction.The excessenthalpies were measured n a mixture-displacement calorimeter with asemi-automatic control constructed by P rofessor R. H. Stokes in Armidale.4 Bothexothermic and endothermic mode of operations were used. The mixing-vesselvolume was about 29 cm3.Prior to a run both substances were degassed.The liquid in the burette was theninjected into the mixing vessel n pulses of 0.002 cm3. In the initial stages readingswere taken at intervals of 0.25 cm3 increasing gradually to a maximum of 2.00 cm3towards the end of the run. The total volume added from the burette to cover thewhole mole-fraction range with reasonable overlap was about 25 cm3 when waterwas added, and 29 cm3 when acetone was in the burette.The semi-automatic control of the rate of injection worked very well in the largepart of the run, manual operation being needed only in the cross-over betweenendothermic and exothermic regions. The calorimeter was immersed in a water bathcontrolled to F0.002 K. All temperature measurements were based on IPTS-68.

3. Results and discussionThe densities of acetone at various temperatures are given in table 1. Literaturevalues are included for comparisons. The densities of water were those of Ke11.8It can be seen that some of the older literature values of the acetone densities aresignificantly higher than those obtained in this work and by Stokes.@The highervalues are most likely due to the presence of water in the acetone.The liquid compositions and excessenthalpies were calculated using the methoddescribed in reference 9. Taking substance 1 to be the one injected into the vesselinitially filled with substance 2, the following equation permits the calculation of thecomposition of the liquid in the calorimeter vessel:

ln(n,/n,,i) = - s (Vi/I: V,)da, (1)0where n, is the amount of substance 2 present in the vessel,n,,, is the initial amountof substance 2, V, is the partial molar volume and FT is the molar volume ofsubstance 1, V, is the volume of the mixing cell, and u is the volume of substance 1added since the start of a run. (The above equation was taken from equation (4) ofreference 9, in which V;Cwas erroneously printed instead of VT.)


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H:{xCH,COCH,+(l -x)H,O} 803With the mixture-displacement calorimeter, the quantities obtained experimentallywere the partial excess enthalpies of the substance in the burette. The measured

enthalpies were first fitted by the least-squares technique to the equation:HF/(J+mol-) = (l-x,) i ,$(1-2x,), (2)

i=O

where x1 is the mole fraction of substance 1 at the mid-point of each increment. Bymeans of the Gibbs-Duhem equation in a modified form:@lx; = (H:-x,~H#Lx,}/~;, (3)

equation (2) can be integrated toHE/(J.moll) = -(x2/2) i (k,/(i+ l)}(l -2x1)+. (4)i=O

Equation (4) permits the calculation of HL from HF, and HF is calculated from HEand Hy.For the whole mole-fraction range at a fixed temperature, two runs were made,starting with one of the two pure substances n the calorimeter. Consequently twosets of calculations were required starting from the ends of the mole-fraction range.Once these were completed the excessmolar enthalpies were combined and re-fittedto the equation:H$/(J . mall ) = x( 1 x) i ai( 1-2x), (5)

i=Ousing the least-squares technique.The excess molar enthalpies, and the partial excess molar enthalpies of eachsubstance are given in table 2. In the above calculation the excessmolar volumes ofthe mixtures were needed. They were taken from those reported by Dizechi andMarschall.() The inclusion of the excess molar volumes made a difference of atmost 1 per cent to the excessmolar enthalpies.For the sake of consistency, the partial molar excessenthalpies reported in table 2are those derived from the final fitting equation (5), as the measured values coveronly half the composition range for each substance. The uncertainty in these partialmolar values may be estimated as + 1 per cent for large values to f 2 J. mol- l forsmaller values.

TABLE 1. Densities of acetoneSource T/K Source

278.15288.15298. 5

0.80677 Present work0.79571 Present work0.79574 Reference 50.78437 Present work0.78432 Reference 6

298.15308.15318.15323.15

0.78433 Reference 70.78502 Reference 50.77281 Reference60.76104 Reference 60.75504 Reference6


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804TABLE

H. T. FRENCHExcess molar enthalpies and partial excess molar enthalpies for/xCH,COCH, (A)+(1 -x)H,O (B)}

X .-.sLJ.mol- HIJ.mol 0.0019 -24 - 123540.0061 -73 - 114240.0104 -122 - 1089600147 -168 - 105840.0190 -213 - 101060.0255 -276 -95410.0342 -353 - 85330.043 1 -424 -75910.0522 -487 - 67000.0613 -544 - 59010.0704 -592 - 52800.0797 -636 -46750.0887 -672 -37740.1024 -715 -33280.1215 -762 -25210.1414 -792 - 18450.1618 -810 -13070.1820 -817 -8930.2025 -815 -5540.2233 - 805 -2820.2440 -788 -600.2597 -771 690.2707 -758 155

0.0020 -22 -111100.0060 -65 - 103430.0103 -109 -99380.0147 -152 -95930.0190 -192 - 90850.0255 -249 - 84680.0343 -319 -76910.0432 -383 - 69000.0524 -442 -61290.0616 -493 -53840.0708 -538 -47800.0801 - 578 -41670.0890 -611 -35930.0957 -633 - 36220.1057 - 660 - 28280.1227 -696 -21840.1425 -723 - 15910.1629 -737 - 10860.1817 -740 - 7070.1949 -738 -4990.2059 -734 -3570.2168 -727 -2100.2264 -720 -990.2349 -713 -220.2475 -701 1100.2676 -677 262

T= 278.15 K0 0.2654-2 0.2817-6 0.2995-13 0.3192-21 0.3396-38 0.3620-66 0.3879- 102 0.4167-144 0.4495

-191 0.4868-241 0.5294- 294 0.5715-345 0.6121-423 0.6504-527 0.6844- 625 0.7212-714 0.7627-796 0.8087-876 0.8486-954 0.8857- 1027 0.9225- 1071 0.9532- 1091 0.9841T=288.15K

0 0.1645-2 0.1728-6 0.1819-12 0.1916-19 0.2020-34 0.2132-60 0.2254-91 0.2383-128 0.2525-170 0.2679-214 0.2852-261 0.3039- 308 0.3237-343 0.3458-396 0.3705-483 0.3983- 580 0.4293-671 0.4639-747 0.5037- 796 0.5433-834 0.5814-870 0.6171-900 0.6477-927 0.6810-964 0.7186- 1022 0.7596

HEJ,mol- HE HBJ.molV FiGi=

-753 169 - 1076-731 281 -1117- 705 381 -1153-673 469 - 1206-638 541 - 1212-596 602 - 1283-547 656 -1323-489 699 - 1352-421 732 - 1379-342 753 -1394-251 758 - 1390- 161 743 -1359-77 711 - 1320-1 666 - 122361 614 -1121122 546 -980178 458 -727221 351 -358238 255 141230 167 716195 88 1501140 36 223556 5 3249

-732 - 1084 -675-734 -904 - 708-735 -727 -741-734 -554 - 776-731 -392 -814-725 -236 -848-716 -89 -885-704 47 -931-689 174 -981- 670 289 -1015-646 397 - 1062-618 491 -1102-585 571 -1144- 546 642 -1174-500 701 -1218-446 751 - 1249-383 788 - 1278-311 813 -1264-227 820 - 1284-144 809 - 1269-66 780 - 12365 739 -118562 694 -1091119 635 -999175 559 -812224 468 -559


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H:{xCH,COCH,+(l -x)H,O)TABLE 2-continued

805

x H: HE fG Xl Hf HBt-J.mol- J,moi- J.mol- x I mol J.mol-l J.molk0.7965 254 3810.8194 265 3250.8399 269 2750.8660 265 213

0.0019 -19 - 104350.0060 -59 -92800.0103 -100 -89640.0147 -139 - 86080.0191 -176 -81390.0256 -226 -76150.0344 -289 - 68240.0435 -346 -60830.0525 - 397 - 53970.0617 -442 -47390.0711 -482 -41520.0807 -517 -35940.0902 - 546 -30920.1045 -582 - 24960.1241 -616 -17900.1450 -637 -11690.1653 - 645 -8120.1853 - 643 -4190.2058 -633 -1410.2183 -624 00.2294 -615 1020.2496 - 594 2720.2715 -567 4090.1670 -641 -8190.1759 -642 -6420.1852 -641 -4710.1950 -638 - 3080.0019 -16 -86050.0060 -51 -81560.0104 -86 - 79080.0147 -119 -75350.0191 -151 - 70840.0257 -197 -65990.0345 -251 - 58960.0436 -301 - 52430.0528 -345 -46010.0620 -384 -40220.0713 -417 -35060.0808 -446 - 2965 0.0906 -471 -26050.1052 -501 -20370.1248 -527 - 14080.1443 -541 -9170.1594 - 545 -6050.1688 - 542 -486

-253 0.892161 0.9214204 0.9535583 0.9849T=298.15 K0 0.2058-2 0.2174-6 0.23OQ-12 0.2437-20 0.2585-34 0.2747-59 0.2921-88 0.3113-122 0.3324-160 0.3555-200 0.3816-244 0.4113-289 0.4446-356 0.4828-449 0.5237-542 0.5634-625 0.6046-697 0.6427-761 0.6759- 795 0.7129- 824 0.7519-875 0.7950-937 0.8458-628 0.8884-659 0.9184-692 0.9504- 728 0.9833

T=308.15 K0 0.1776-2 0.1872-5 0.1976-9 0.2086-15 0.2205-28 0.2335-49 0.2475-77 0.2626- 108 0.2793-144 0.2975-181 0.3175- 220 0.3397-261 0.3639-322 0.3913-401 0.4224-477 0.4571- 534 0.4967- 560 0.5428

248 153 1060213 91 1655150 37 243057 4 3513

-633 -150 - 760-625 1 -795-613 144 -832- 599 276 -872- 580 397 -906-558 505 -947-531 600 -983-499 682 - 1015-462 750 - 1058-419 804 - 1093-368 846 -1131- 309 876 -1148-242 892 -1163-164 895 -- 1167-80 881 - 1137-1 854 -110377 808 -1040145 750 -944198 688 - 799249 605 -631291 506 - 369317 388 78316 249 636281 143 1327234 81 2003I62 32 27126 4 3452

-541 -333 -591-538 -183 - 620-532 -38 -656- 524 99 -690-514 228 -724-501 350 -751-484 462 - 792-464 562 -823-440 655 -857-411 735 - 890-377 804 -925-338 861 -963-293 906 -988-241 941 -1006-180 964 -1019-111 974 - 1028-32 968 -100959 939 -991


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806 H. T. FRENCHTABLE Z-continued

x Hii Hi HB X fCl H:J.molV J.mol- J.molk HBE--J.molk J.mol- J,mol-0.5953 156 8780.6407 233 8010.6756 285 7270.7450 359 549

-882 0.8389-782 0.9040-637 0.948 1-222 0.9820T= 318.15 K

372 281 874295 117 1978190 38 294975 5 3901

0.0042 -32 -73110.0105 -77 -68390.0149 -106 - 65300.0193 -133 -61530.0236 -159 -58630.0303 - 196 -53700.0393 -241 -47130.0484 -281 -39850.0577 -315 -36210.0671 -345 -31020.0768 -371 -26180.0867 -393 -21550.0964 -410 -18480.1113 -429 -13590.1314 -443 -8190.1516 -447 -4060.1766 -440 00.1977 -426 2200.2145 -411 4170.2366 -385 5890.2586 -354 7290.2803 -321 8360.1616 -439 -2370.1705 -436 -920.1795 -432 390.1892 -425 1680.1997 -417 292

-1 0.2111-5 0.2235-9 0.2369-15 0.2513-22 0.2672-36 0.2845-58 0.3033-85 0.3243-115 0.3476-149 0.3733- 185 0.4021-223 0.4349-260 0.4719-316 0.5139-388 0.5568-454 0.5985-528 0.6365-587 0.6712-632 0.7047

-689 0.7447-738 0.7942- 766 0.8437-485 0.8873-517 0.9191- 539 0.9525- 569 0.9846-598

-406 409 -626-392 520 -643-376 622 -676-356 716 - 707-332 801 -736-304 876 -767-273 940 - 802-235 995 - 829-192 1039 -856- 143 1072 -875-87 1093 -885-21 1100 -88952 1089 -874133 1056 -839212 1000 -767283 926 -675340 844 -547384 758 -385417 668 - 183

443 555 130450 411 582422 271 1241362 160 1943294 91 2647196 35 338872 4 4404T= 323.15 K

0.0020 -15 - 7025 0 0.1874 -370 268 - 5260.0062 -43 - 6688 -2 0.1975 - 362 381 -5520.0105 -71 -6362 -5 0.2089 -350 495 -5710.0150 -98 -6049 -9 0.2216 -336 605 -6040.0197 -126 -5566 -16 0.2349 -319 703 -6320.0262 -161 - 5059 -27 0.2491 -299 792 -6570.0348 -202 -4531 -46 0.2647 -275 872 -6890.0439 -240 -4008 -70 0.2821 - 247 945 -7090.0532 -273 - 3428 -98 0.3003 -216 1004 -7350.0627 - 302 -2878 -128 0.3206 -180 1055 - 7630.0722 -326 - 2449 -160 0.3442 -136 1097 -7790.0820 -347 -2012 - 193 0.3701 -87 1126 -8050.0920 -363 -1749 -227 0.3990 -31 1143 - 8060.1070 -382 - 1294 -277 0.4322 34 1145 -8150.1266 -396 -761 -340 0.4695 106 1128 - 8060.1472 -400 -363 -402 0.5116 186 1088 - 7630.1646 -396 -121 -452 0.5543 262 1027 -6910.1743 -392 0 -478 0.5948 328 950 -5810.1884 -384 170 -511 0.6324 382 865 -439


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H$CH,COCH,+(l- x)HzO;TABLE 2-continued

807

Y f&t Hi HB" Y Xl HF4 HB"J,mol- J.mol-I J.mol J,molF J.molF J.rnol~ 0.6667 423 776 -280 0.8870 373 151 21150.6961 450 695 -110 0.9 182 302 86 21140.7360 474 577 189 0.9504 04 34 34660.7923 477 408 720 0.9831 78 4 43370.8447 439 258 1431

Errors in the measured Hf: values are mainly due to not quite restoring the vesselto the baseline temperature at the end of a step. The effect,of such errors on Hz islargely cancelled in the following step. The uncertainty in the mole fraction is+O.OOOl.The parameters for equation (5) are given in table 3.Figures 1 and 2 show the excessmolar enthalpies of (acetone + water) at 298.15and 323.15 K respectively. The more recent literature values are included forcomparisons. In general the agreement between the results from the present workand the literature values is poor, with the exception of those reported by Belousovand Sokolova.) Quite good agreement was obtained with their results at both308.15 and 323.15 K.It can be seen n figure 1 that the disagreement with Coomber and Wormalds12results at 298.15 K occurred mainly in the exothermic region. This was probablycaused by the different methods in which the exothermic run was done. In thepresent work isothermal conditions were maintained in both endothermic andexothermic runs, in the latter by means of a Peltier diode. Coomber and Wormaldi2allowed their mixtures to increase their temperatures, the excess enthalpies beingcalculated from the deflection of the chart recorder attached to the calorimeterthermocouple. It was possible that this procedure introduced a significantuncertainty to their results.The disagreement between the present results and those of Villamanan and VanNessf3)occurs mainly in the endothermic region; up to x z 0.2 the two sets of resultsagree well. The cause for the discrepancy in this case was probably the presence of

TABLE 3. Parameters of equation: Hk/(J mol I) = u( 1 - u) i ai( 1 -2.x) and standard deviations ,TI =oTK 278.1500 -1257UI -430602 - 1016a3 - 239604 - 199705 - 1515s 2.8

288.15 298.15 308. I5 318.15 323.15- 942.2 - 520. I - 103.5 423.8 655.9-4231 -4137 -3996 -3878 -3741- 905.6 - 665.2 -419.5 431.2 - 324.8- 2032 - 1915 - 1732 -1355 -1398- 1749 - 1859 -1662 ~ 1405 -1503- 1472 - 1097 - 990.3 -1177 -914.

2.0 2.0 1.1 2.7 2.4


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1I t I I I0 0.2 0.4 0.6 0.8XFIGURE 1. Excess molar enthalpies for {xCH,COCH,+(l -x)H,O} at 298.15K. 0, This work;l , reference 12; A, reference 13; + , reference 14; x , reference 15.

XFIGURE 2. Excess molar enthalpies for {xCH,COCH3+(l -x)H,O) at 323.15K. 0, This work;x1 reference3; 0. reference 11.


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H:{xCH,COCH,+(l -.x)H,O] 809water impurity in Villamanan and Van Nesss acetone which had an assay of 99.5moles per cent.

The presence of a small amount of water as impurity in the acetone has a largeeffect on the molar excessenthalpies at the acetone-rich end due to two contributingfactors. Firstly, even though the level of impurity is low, the additional water fromthe impurity changes its mole fraction to a significant extent. For example 0.5 moleper cent of water in the acetone will increase (1 -x) from 0.020 to 0.025. Secondly, therate of change of the excessmolar enthalpies as more water is added is high at thisend of the mole-fraction range: about 3 to 4 kJ. mol- . A large change in Hi isbrought about by a small change in x; 0.5 mole per cent of water impurity increasesHz by 15 to 20 J.mol- at x ~0.98.At the water-rich end the contribution made by the water impurity to the overallmole fraction of water is insignificant, and the partial molar excess enthalpies ofwater are small. The effect of the impurity on HE is therefore negligible.I thank Professor R. H. S tokes for the loan of the apparatus and for his invaluablehelp.REFERENCES

1. Woolf, L. A. to be published.2. Christensen, J. J.; Hanks, R. W.; Izett. R . M. Handbook of Heats of Mixing. Wiley: New York. 1982,pp. 1458.3. Villamanan, M. A.; Van Ness, H. C. J. Chem. Eng. Data 1984, 29, 429.4. Stokes, R. H. J. Chem. Thermodynamics 1988, 20, 1349.5. Timmermanns, J. Physico-chemical Constants of Binary Systems. Interscience: New York. 1950,p. 355.6. Stokes, R. H. personal communications.7. Evans, D. F.; McElroy, M. I. J. Solufion Chem. 1975, 4, 413.8. Kell, G. S. J. Phys. Chem. Ref Data 1977, 6. 1109.9. Stokes, R. H. J. Chem. Thermodynamics 1986, 18, 359.IO. Dizechi, M.; Marschall, E. J. Chem. Eng. Data 1982, 27, 358.Il. Belousov, V. P.; Sokolova, E. P. Vestn. Leningrad Univ., Fii. Khim. 1966, 2 1, 90.12. Coomber, B. A.; Wormald, C. J. J. Chem. Thermodynamics 1976, 8, 793.13. Drinkard, W.; Kivelson, D. J. Phys. Chem. 1 %8,62, 1494.14. Kister, A. T.; Waldman, D. C. J. Phys. Chem. 1958, 62, 245.15. Hanson, D. 0.; Van Winkle, M. J. Chem. Eng. Data 1960, 5. 30.

Excess enthalpies of (acetone + water) at 278.15, 288.15, 298.15, 308.15, 318.15, and 323.15 K

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