已知P-R方程为 p?（1）
其中 b?0.077796RTc8.314?305.4?6?0.077796??40.44?10 6pc4.884?10RTa? V?bV(V?b)?b(V?b)(RTc)2(8.314?305.4)2ac?0.457235?0.457235??0.6036 6pc4.884?10
m?0.3746?1.54226??0.26992?2?0.37646?1.54226?0.098?0.26992?(0.098)2?0.5250 a0.5?1?m(1?Tr0.5)?1?0.5250?[1?(1.20)0.5]?0.9499 a=aca?0.6036?(0.9499)2?0.5446 将方程（1）化成压缩因子形式，得
Z3?(1?B)Z2?(A?2B?3B2)Z?(AB?B2?B3)?0 （2）
ap0.5446?3446?103??0.2021 其中 A=
(RT)2(8.314?366.48)2bp40.44?10?6?3446?103??0.0457 B=RT8.314?366.48将A，B之值代入式（2）中，得
2 Z3?(1?0.0457)Z2??(0.2021?2?0.0457?3(0.0457))???Z
23??(0.02021?0.0457?(0.0457)?(0.0457))????0
化简上式，得
Z3?0.9543Z2?0.1044Z?0.0071?0
迭代求解此方程，得
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Z=0.8741
因而
V?ZRT0.8741?8.314?366.4833??0.000773(m/mol)?0.02570m/kg 3p3446?10其文献值的相对百分偏差为
??0.02570?0.02527?100%??1.70%
0.02527
2-24. 估算150℃时乙硫醇的液体摩尔体积。已知实验值为0.095m3?kmol-1。乙硫醇的物性为TC pC?5.49 MPa， ??0.190，VC?0.207m3?kmol-1 ，200C?499?，
的饱和液体密度为839kg?m3。
解：用改进的Rackett方程
200C时： M乙硫醇?62.137 TrR? V293R?M293?0.5875 499??62.134?0.07406m3kmol?1 做参比 839 V?V293RZcr? ，
Zcr?0.29058?0.08775??0.2739
???1?Tr??1?Tr722???R?272 ??1?0.848?7??1?0.587?7
??0.1927 V?0.07406?0.2739?0.1927?0.09505m3?kmol?1
误差：0.05%
2-25. 估算20oC氨蒸发时的体积变化。此温度下氨的蒸气压为857 kPa。
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解：Tc=405.7K T=293.15K
T Tr=0.723 Tr?TcP Pr=0.076 pr?PcPc=112.8bar P=857KPa
Vc=72.5cm3?mol-1 Zc=0.242 ?=0.253 V?VCZCsl?1?Tr?2/7 Vsl=27.11cm3?mol-1
B0=-0.627
B0?0.083?0.422Tr1.6B1?0.139?0.172 B1=-0.534 Tr4.2V=sv
TRTsv
?(B0??B1)RC V =2616cm3?mol-1 PPC△V= Vsv - Vsl △V=2589cm3?mol-1
或者：Z0=0.929 Z1=-0.071 Z= Z0 +?Z1 Z=0.911 Vsv =
ZRT Vsv =2591cm3?mol-1 P△V= Vsv - Vsl △V=2564cm3?mol-1
2-26. 某企业需要等摩尔氮气和甲烷的混合气体4.5kg，为了减少运输成本，需要将该气体在等温下从0.10133 MPa，-17.78 ℃压缩到5.0665 MPa。现在等温下将压力提高50倍，问体积能缩小多少倍？ （试用普遍化第二维里系数的关系）
解：设N2与甲烷的摩尔数都为n，则
28n+16n=4.5×103 解得n=102.3mol
T?273.15?17.78?255.37K
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51)p1?1.013?10Pa,T1?255.37K时
0?0.083?CH4: B110.4220.422?0.083???0.181 1.61.6Tr(1.34)1B11?0.139?0.1720.172?0.139??0.0887 4.24.2Tr(1.34)RTC8.314?190.601?53B11?（B11??B11）?（?0.181?0.008?(0.0887)??6.21?10m/mol6PC4.6?100?0.083?N2: B220.4220.422?0.083???0.054 1.61.6Tr(2.02)1B22?0.139?0.1720.172?0.139??0.130 4.24.2Tr(2.02)B22?RT22C8.314?126.2（B220??B221）?（?0.054?0.04?(0.13)??1.51?10?5m3/mol6P22C3.394?10? i12?(?1??2)/2?(0.008?0.04)/2?0.024Tc12?(Tc11?Tc22)0.5(1?k12)?(190.6?126.2)0.5?155.1K
Tr12=T/Tc12=255.37/155.1=1.65
Vc12?(31/3 Vc1/11?Vc22
Pc 12?2?(99?10?6)1/3?(89.5?10?6)1/3?3?53)????9.42?10m/mol2??3Zc12RTc120.289?8.314?155.1??3.96MPaVc129.42?10?5B1200.4220.422?0.083?1.6?0.083???0.107Tr(1.65)1.6
B121?0.139?0.1720.172?0.139??0.1184.24.2Tr(1.65)
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