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Osmotic coefficient

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is slightly greater than that predicted by Raoult's law up to a concentration of 0.7 mol/kg, after which the vapor pressure is lower than Raoult's law predicts. For aqueous solutions, the osmotic coefficients can be calculated theoretically by
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Ge, Xinlei; Zhang, Mei; Guo, Min; Wang, Xidong (2008). "Correlation and Prediction of Thermodynamic Properties of Some Complex Aqueous Electrolytes by the Modified Three-Characteristic-Parameter Correlation Model".
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Ge, Xinlei; Wang, Xidong; Zhang, Mei; Seetharaman, Seshadri (2007). "Correlation and Prediction of Activity and Osmotic Coefficients of Aqueous Electrolytes at 298.15 K by the Modified TCPC Model".
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Ge, Xinlei; Zhang, Mei; Guo, Min; Wang, Xidong (2008). "Correlation and Prediction of Thermodynamic Properties of Nonaqueous Electrolytes by the Modified TCPC Model".
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This means that, at least at low concentrations, the vapor pressure of the solvent will be greater than that predicted by Raoult's law. For instance, for solutions of
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Ge, Xinlei; Wang, Xidong (2009). "A Simple Two-Parameter Correlation Model for Aqueous Electrolyte Solutions across a Wide Range of Temperatures†".
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In a single solute solution, the (molality based) osmotic coefficient and the solute activity coefficient
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and there is thus a differential relationship between them (temperature and pressure held constant):
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the two definitions are similar, and in fact both approach 1 as the concentration goes to zero.
1383: 521: 495:{\displaystyle \ln x_{A}=-\ln \left(1+M_{A}\sum _{i}m_{i}\right)\approx -M_{A}\sum _{i}m_{i},} 296: 1373: 535: 1388: 969: 942: 558: 513: 55: 25: 922: 8: 1337: 524:, allows calculation of the salt activity coefficient through the osmotic coefficient. 321: 290: 54:. It can be also applied to solutes. Its definition depends on the ways of expressing 1625: 1590: 1554: 1519: 1466: 1074:{\displaystyle \phi =1+{\frac {1}{m}}\int _{0}^{m}md\left(\ln(\gamma _{\pm })\right)} 1417: 1617: 1582: 1546: 1511: 1490: 1421: 1412: 1358: 1346: 512:
For liquid solutions, the osmotic coefficient is often used to calculate the salt
1378: 1368: 1363: 51: 1341: 1326: 1200:{\displaystyle \ln(\gamma _{\pm })=\phi -1+\int _{0}^{m}{\frac {\phi -1}{m}}dm} 47: 1643: 1629: 1594: 1558: 1523: 1416:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) " 1333:
is the Debye–Hückel constant (equal to about 1.17 for water at 25 °C).
343: 166: 1425: 156:{\displaystyle \phi ={\frac {\mu _{A}^{*}-\mu _{A}}{RTM_{A}\sum _{i}m_{i}}}} 351: 359: 1267: 332: 1621: 1586: 1550: 1515: 16:
Quantity characterizing the deviation of a solvent from ideal behavior
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measurements, or measurements of deviations from ideality for other
248:{\displaystyle \phi =-{\frac {\mu _{A}^{*}-\mu _{A}}{RT\ln x_{A}}}} 62: 43: 363: 370:. The values for the two definitions are different, but since 986:
can be calculated from the salt activity coefficient via:
366:. The latter osmotic coefficient is sometimes called the 665:{\displaystyle RTm(1-\phi )=G^{E}-m{\frac {dG^{E}}{dm}}} 1487:
Guidelines for the extrapolation to zero ionic strength
912:{\displaystyle \phi ={\frac {-\ln(a_{A})}{\nu mM_{A}}}} 516:
from the solvent activity, or vice versa. For example,
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is a quantity which characterises the deviation of a
28: 1313: 1258: 1199: 1103: 1073: 978: 958: 931: 911: 839: 801: 728:{\displaystyle RT\ln \gamma ={\frac {dG^{E}}{dm}}} 727: 664: 574: 544: 494: 312: 281: 247: 155: 34: 1641: 1491:http://www.nea.fr/html/dbtdb/guidelines/tdb2.pdf 1214:, which is accurate only at low concentrations, 1084:Moreover, the activity coefficient of the salt 812: 527: 1571: 1536: 1459:Activity Coefficients in Electrolyte Solutions 1440:Activity Coefficients in Electrolyte Solutions 817:For a single salt solute with molal activity ( 847:), the osmotic coefficient can be written as 802:{\displaystyle d((\phi -1)m)=md(\ln \gamma )} 1610:Journal of Chemical & Engineering Data 1575:Journal of Chemical & Engineering Data 1539:Journal of Chemical & Engineering Data 1504:Journal of Chemical & Engineering Data 1601: 939:is the stochiometric number of salt and 1642: 1607: 1456: 1436: 1479: 1314:{\textstyle -{\frac {2}{3}}AI^{3/2}} 1259:{\textstyle (\phi -1)\sum _{i}m_{i}} 13: 1413:Compendium of Chemical Terminology 14: 1661: 61:The osmotic coefficient based on 840:{\displaystyle \gamma _{\pm }m} 507: 1565: 1530: 1495: 1450: 1430: 1401: 1233: 1221: 1140: 1127: 1104:{\displaystyle \gamma _{\pm }} 1063: 1050: 885: 872: 796: 784: 772: 766: 754: 751: 613: 601: 324:of the solvent in a solution, 1: 1394: 966:the activity of the solvent. 813:Liquid electrolyte solutions 528:Relation to other quantities 368:rational osmotic coefficient 282:{\displaystyle \mu _{A}^{*}} 7: 1437:Pitzer, Kenneth S. (2018). 1352: 10: 1666: 1485:I. Grenthe and H. Wanner, 518:freezing point depression 1457:Pitzer, Kenneth (1991). 1111:can be calculated from: 554:excess Gibbs free energy 313:{\displaystyle \mu _{A}} 293:of the pure solvent and 1426:10.1351/goldbook.O04342 545:{\displaystyle \gamma } 1384:Thermodynamic activity 1315: 1260: 1201: 1105: 1075: 980: 960: 933: 913: 841: 803: 729: 666: 576: 546: 522:colligative properties 496: 314: 283: 249: 157: 36: 1316: 1261: 1202: 1106: 1076: 981: 979:{\displaystyle \phi } 961: 959:{\displaystyle a_{A}} 934: 914: 842: 804: 730: 667: 577: 575:{\displaystyle G^{E}} 547: 497: 315: 284: 250: 158: 37: 35:{\displaystyle \phi } 1389:Ion transport number 1274: 1218: 1118: 1088: 993: 970: 943: 932:{\displaystyle \nu } 923: 851: 821: 745: 677: 589: 559: 536: 514:activity coefficient 376: 297: 261: 175: 72: 56:chemical composition 26: 1418:osmotic coefficient 1212:Debye–Hückel theory 1172: 1032: 552:are related to the 278: 204: 98: 21:osmotic coefficient 1650:Physical chemistry 1374:van 't Hoff factor 1338:magnesium chloride 1311: 1256: 1245: 1197: 1158: 1101: 1071: 1018: 976: 956: 929: 909: 837: 799: 725: 662: 582:by the relations: 572: 542: 492: 478: 437: 322:chemical potential 310: 291:chemical potential 279: 264: 245: 190: 153: 139: 84: 32: 1622:10.1021/je800483q 1587:10.1021/je7006499 1551:10.1021/je700446q 1516:10.1021/je060451k 1472:978-1-315-89037-1 1288: 1236: 1189: 1016: 907: 723: 660: 469: 428: 243: 151: 130: 1657: 1634: 1633: 1605: 1599: 1598: 1569: 1563: 1562: 1534: 1528: 1527: 1499: 1493: 1483: 1477: 1476: 1454: 1448: 1447: 1445: 1434: 1428: 1405: 1359:Bromley equation 1347:Pitzer equations 1320: 1318: 1317: 1312: 1310: 1309: 1305: 1289: 1281: 1265: 1263: 1262: 1257: 1255: 1254: 1244: 1206: 1204: 1203: 1198: 1190: 1185: 1174: 1171: 1166: 1139: 1138: 1110: 1108: 1107: 1102: 1100: 1099: 1080: 1078: 1077: 1072: 1070: 1066: 1062: 1061: 1031: 1026: 1017: 1009: 985: 983: 982: 977: 965: 963: 962: 957: 955: 954: 938: 936: 935: 930: 918: 916: 915: 910: 908: 906: 905: 904: 888: 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CRC Press. 1439: 1432: 1411: 1403: 1335: 1330: 1322: 1209: 1083: 816: 737: 531: 511: 508:Applications 503: 372: 367: 355: 352:gas constant 347: 336: 325: 256: 171: 164: 65: 60: 52:Raoult's law 20: 18: 360:temperature 1395:References 1268:asymptotic 333:molar mass 169:basis by: 1630:0021-9568 1595:0021-9568 1559:0021-9568 1524:0021-9568 1463:CRC Press 1278:− 1238:∑ 1228:− 1225:ϕ 1180:− 1177:ϕ 1160:∫ 1150:− 1147:ϕ 1136:± 1132:γ 1125:⁡ 1097:± 1093:γ 1059:± 1055:γ 1048:⁡ 1020:∫ 997:ϕ 974:ϕ 927:ν 891:ν 870:⁡ 864:− 855:ϕ 830:± 826:γ 794:γ 791:⁡ 761:− 758:ϕ 693:γ 690:⁡ 630:− 611:ϕ 608:− 540:γ 471:∑ 457:− 454:≈ 430:∑ 405:⁡ 399:− 383:⁡ 302:μ 275:∗ 266:μ 230:⁡ 210:μ 206:− 201:∗ 192:μ 185:− 179:ϕ 165:and on a 132:∑ 104:μ 100:− 95:∗ 86:μ 76:ϕ 30:ϕ 1644:Category 1353:See also 1321:, where 63:molality 331:is its 320:is the 289:is the 44:solvent 1628:  1593:  1557:  1522:  1469:  1340:, the 919:where 364:Kelvin 257:where 1444:(PDF) 1408:IUPAC 46:from 1626:ISSN 1591:ISSN 1555:ISSN 1520:ISSN 1467:ISBN 1329:and 358:the 354:and 350:the 342:its 1618:doi 1583:doi 1547:doi 1512:doi 1489:, 1422:doi 1420:". 1325:is 1270:to 1266:is 362:in 19:An 1646:: 1624:. 1614:54 1612:. 1589:. 1579:53 1577:. 1553:. 1543:53 1541:. 1518:. 1508:52 1506:. 1461:. 1410:, 1122:ln 1045:ln 867:ln 788:ln 687:ln 402:ln 380:ln 346:, 335:, 227:ln 1632:. 1620:: 1597:. 1585:: 1561:. 1549:: 1526:. 1514:: 1475:. 1424:: 1331:A 1323:I 1307:2 1303:/ 1299:3 1295:I 1291:A 1286:3 1283:2 1252:i 1248:m 1242:i 1234:) 1231:1 1222:( 1195:m 1192:d 1187:m 1183:1 1169:m 1164:0 1156:+ 1153:1 1144:= 1141:) 1128:( 1068:) 1064:) 1051:( 1041:( 1037:d 1034:m 1029:m 1024:0 1014:m 1011:1 1006:+ 1003:1 1000:= 952:A 948:a 902:A 898:M 894:m 886:) 881:A 877:a 873:( 858:= 835:m 797:) 785:( 782:d 779:m 776:= 773:) 770:m 767:) 764:1 755:( 752:( 749:d 720:m 717:d 710:E 706:G 702:d 696:= 684:T 681:R 657:m 654:d 647:E 643:G 639:d 633:m 625:E 621:G 617:= 614:) 605:1 602:( 599:m 596:T 593:R 568:E 564:G 490:, 485:i 481:m 475:i 465:A 461:M 450:) 444:i 440:m 434:i 424:A 420:M 416:+ 413:1 409:( 396:= 391:A 387:x 356:T 348:R 340:A 337:x 329:A 326:M 306:A 270:A 238:A 234:x 224:T 221:R 214:A 196:A 182:= 146:i 142:m 136:i 126:A 122:M 118:T 115:R 108:A 90:A 79:= 66:m

Index

solvent
ideal behaviour
Raoult's law
chemical composition
molality
mole fraction
chemical potential
chemical potential
molar mass
mole fraction
gas constant
temperature
Kelvin
activity coefficient
freezing point depression
colligative properties
excess Gibbs free energy
Debye–Hückel theory
asymptotic
ionic strength
magnesium chloride
vapor pressure
Pitzer equations
Bromley equation
Pitzer equation
Davies equation
van 't Hoff factor
Law of dilution
Thermodynamic activity
Ion transport number

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