由理想气体方程式得 RT RT RT …,P1= ∑P,=∑ RTRT P总.即P 2.表达 P 文字叙述:在温度和体积恒定时,其总压力等于各组分气体单独存在时的压力之和 4.另一种表达形式:B、 mole fraction RT 在温度和体积恒定时,理想气体混合物中,各组分气体的分压(p)等于总压(P总) 乘以该组分的摩尔分数(x) 5.实验证明: Ramsay(1852-1916)- British chemist,荣获1904 Nobel chemical prize 如左图:Pd制小管只允许氢气通过,而不许 氩气通过。在外管通入一定压强的氢气,平衡 后,P1=PAx+P1,。不断改变氢气的压强 (P1,、P1,),则pr=p p1=p+p1,,P关系式不变,从而验证 Fig. 1.8 Ramsay's apparatus of verifying the law 了 Dalton分压定律 6. Application of Dalton's law of partial pressures (1)求分压: Sample Exercise 1: Suppose that hydrogen is collected over water at 25C. How much H2 (expressed in moles) has been collected when the volume of gas is 223 ml under atmospheric pressure of 74.2 cm Hg? Solution: Patm= PH. t PH o, Pam=74.2 cm Hg The vapor pressure of water at 25C is 23. 8 mmHg(2. 38 cm Hg) PH= Patm-PHo =74.2-2.4=71.8cmHg Solving the ideal gas equation for n, we find p(71.8/760)×0.223 =861×10-3(mol RT008206×29815 (2)求转化率: Sample Exercise2:已知某温度、lam下,AB2(g)在密闭容中进行如下分解 A4 B2(9)= 2A2(g)+ B2(g 达到平衡时,容器的压力为14atm,求A4B2的转化率为多少?10 由理想气体方程式得： 1 1 RT p n V = ， 2 2 RT p n V = ，……， i i RT p n V = ，……  p总 V RT n V RT  pi = ni = = ，即 p总 =pi 2．表达式： p总 =pi 3．文字叙述：在温度和体积恒定时，其总压力等于各组分气体单独存在时的压力之和。 4．另一种表达形式： i i i i RT n p n V x p n RT n V = = = 总 ─ mole fraction 在温度和体积恒定时，理想气体混合物中，各组分气体的分压（pi）等于总压（p 总） 乘以该组分的摩尔分数（xi）。 5．实验证明：Ramsay (1852－1916) — British chemist, 荣获 1904 Nobel chemical prize 6．Application of Dalton’s law of partial pressures (1) 求分压： Sample Exercise 1：Suppose that hydrogen is collected over water at 25℃ .How much H2 (expressed in moles) has been collected when the volume of gas is 223 ml under atmospheric pressure of 74.2 cm Hg? Solution： 2 2 atm H H O p p p = + ， atm p =74.2 cm Hg The vapor pressure of water at 25℃ is 23.8 mmHg (=2.38 cm Hg)  H atm H O 2 2 p p p = − = − = 74.2 2.4 71.8cmHg Solving the ideal gas equation for n, we find 3 8.61 10 0.08206 298.15 (71.8/ 76.0) 0.223 − =    = = RT pV n (mol) (2) 求转化率： Sample Exercise 2：已知某温度、1atm 下，A4B2(g)在密闭容中进行如下分解 A4B2(g) 2A2(g) + B2(g) 达到平衡时，容器的压力为 1.4atm，求 A4B2 的转化率为多少？ 如左图：Pd 制小管只允许氢气通过，而不许 氩气通过。在外管通入一定压强的氢气，平衡 后， T Ar H2 p p p = + 。不断改变氢气的压强 （ 2 ' Hp 、 2 '' Hp ），则 2 ' ' T Ar H p p p = + ， 2 '' '' T Ar H p p p = + ， T p 关系式不变，从而验证 Fig. 1.8 Ramsay’s apparatus of verifying the law 了 Dalton 分压定律。 of partial pressures