物化第一章.doc

第1章 The properties of gasesNameSymbol,Valuepascal1Pa1Nm-2,1kgm-1s-2bar1bar105paamosphere1atm101325Patorr1torr(101325/760)Pa=133.32Pamillimeter of mercury1mmHg133.322Papound per square inch1psi6.894757kPaExample 1.2 calculating the pressure exerted by a column of liquid Derive an equation for the pressure at the base of a column of liquid of mass density and height h at the surface of the earth.Answer: Let the column have cross-sectional(代表性的)area A ;then its volume is Ah and its mass is m=A h. The force the column of this mass exerts at its base is F=mg=A h gThe pressure at the base of the column is therefore P=F/A=A h g/A=g h (2)两种不同的压力计：封闭型：p=g h 敞开型：p=p ex+g h(3)Temperature:diathermic(透热性) adiabatic(绝热性) Zeroth Law of thermodynamics(热力学第零定律)If A is in thermal equilibrium with B , and B is in thermal equilibrium with C , then C is also in thermal equilibrium with A .Celsius scale(摄氏温标)Thermodynamic temperature scale(热力学温标)Thermodynamic and Celsius temperatures are related by the exact expression:T/K=/+273.15(4)Avogadros principleV=constantn (at constant pressure and temperature)It implies that the volume of a sample of a gas is proportional(成比例)to the amount of molecules present, and that the constant of proportionality is independent of the identity of the gas.The perfect gas equation:PV=nRT R is called gas constantTable 1.2 the gas constant in various unitsR8.31451 J k-1 mol-18.2057810-2 L atm k-1mol-18.3145110-2 L bar K-1 mol-18.31451 Pa m3 K-1 mol-162.364 L Torr K-1 mol-11.98722 cal K-1 mol-1 Standard ambient temperature and pressure:298.15K , 105PaStandard temperature and pressure:273.15K, 1atmCombined gas equation:P1V1/T1=p2V2/T2(5) mixtures of gasesDaltons law :The pressure exerted by a mixture of gases is the sum of the partial pressures of the gases.混全气体的总压力等于各组分单独存在于混合气体的体积和温度条件下的压力总和-道尔顿分压定律P=PA+PB+Mole fractions and partial pressures XJ=nJ/nn=nA+nB+xA+xB+=1(6) Real gases Molecular interactions The compression factor压缩因子The compression factor , Z , of a gas is the ratio its molar volume, Vm ,to the molar volume of a perfect gas ,Vom , at the same pressure and temperature:Z=Vm/Vom（压缩因子与1的偏离反应了气体的可压缩性）PVm=RTZ压缩因子的实验值显示，在低压下，Z1,气体接近于理想气体；在高压下，Z1,摩尔体积比理想气体的大，此时分子间斥力占优势；在中等强度的压力下，大多数气体Z1,吸引力占优势。(7) Virial coefficients 维理系数PVmRT(1+Bp+Cp2+)PVm =RT(1+B/Vm+C/Vm2+)These two expressions are two versions of the virial equation of state . In each case , the term in parentheses (在圆括号中) can be identified with the compression factor , Z .The coefficients B , C , , which depend on the temperature , are the second , third , , virial coefficients ; then first virial coefficient is 1 . The third virial coefficient, C , is usually less important than the second coefficient , B .dZ/dp=B+2Pc+Bas p0dZ/d(1/Vm) B as Vm ,corresponding to p0boyle temperature当温度趋于0K时，压缩因子Z趋于1时的温度称为波义耳温度。用TB 表示。PVmRTB(8) Condensation 冷凝Saturate vapour pressure 饱和蒸气压Relative humidity 相对湿度相对湿度P（蒸气压）/Ps（饱和蒸气压）100%（9）Critical constants 临界常数 The critical point of the gas . the temperature , pressure , and molar volume at the critical point are called the critical temperature ,Tc , critical pressure , Pc , and critical volume ,Vc , of the substance . Tc , Pc and Vc are the critical constants of a substance .At and above Tc ,the sample has a single phase that occupies the entire volume of the container . Such a phase , by definition , a gas . Hence , the liquid phase of a substance does not form above the critical temperature . The single phase that fills the entire volume when T Tc may be much denser than we normally consider typical of gases , and the name supercritical fluid(超临介流体) is preferred .超临介流体在临介点附近其密度与液态的密度数量级类似，而其流动性却更接近气态。物质在超临介状态下可以溶解许多其在液态时不能溶解的物质，而且这种溶解度也随压力的变化会有极大的改变。(10) The vander Waals equationThe vander Waals equation is P=nRT/(V-nb)-a(n/V)2The equation is often written in terms of the molar volume Vm=V/n as P=RT/(Vm-b)-a /Vm 2The constants a and b are called vander Waals coefficients . They are characteristic of each gas but independent of the temperature.(11) The principle of corresponding states 对应状态原理以临界参数为基准，定义对比压力Pr，对比摩尔体积Vr及对比温度Tr:Pr=P/Pc Vr=Vm/Vc Tr=T/Tc对应状态原理：若不同的气体有两个对比状态参数相等，则第三个对比状态参数大体具有相同的值。The observation that real gases at the same reduced volume and reduced temperature exert the same reduced pressure is called the principle of corresponding states.-the principle is only an approximation.PrPc=RTrTc/(VrVc-b)-a/(VrVc)2Then we expressed the critical constants in terms of a and b :aPr/27b2=8aTr/27b(3bVr-b)-a/9b2Vr2Which can be reorganized intoPr=8Tr/(3Vr-1)-3/Vr2-普遍范德华方程This equation has t