化學(xué)反應(yīng)動(dòng)力學(xué)六、七、九章答案(共6頁)

1、精選優(yōu)質(zhì)文檔-傾情為你奉上化學(xué)反應(yīng)動(dòng)力學(xué)第六、七、九章習(xí)題daan1. Calculate k (T) given the following forms for the reactive cross section:(a)R(v) =d2, i.e., a constant. If d is the molecular diameter, this represents an “encounter limited rate coefficient”.(b)R(E) =0 ( 1 - e- a E )Do any of these calculated ks have an Arrhenius

2、-like temperature dependence? 解：（a）反應(yīng)截面與反應(yīng)速率常數(shù)的關(guān)系為： k(u) =R u R 其中，u R：相對平動(dòng)速率解法1：因反應(yīng)截面為常數(shù)，故可先求出平均速率，然后據(jù)k(T) =R <u R>求k(T) 根據(jù)氣體分子運(yùn)動(dòng)論： 其中：Maxwell-Boltzmann分布函數(shù) ：折合質(zhì)量。 則有：k(T) =R<u R>解法2： (b) Arrhenius公式為：，k與T呈指數(shù)關(guān)系，隨T的增加，k呈指數(shù)增長。而(a) k(T)T1/2 ,(b) ,與Arrhenius公式中k與T的關(guān)系不同。2. For a Lennard-Jone

3、s “ 6 - 12 ” potential determine the internuclear distance at the potential energy minimum. 解：Lennard-Jones 勢能函數(shù)為： 其中：Lennard-Jones 勢能函數(shù)的勢阱深度 r ：分子間距離 ：V(r)=0, r時(shí)的r值。 則： 當(dāng)時(shí)，勢能V為最小值， 得： 即，勢能最小時(shí)，核間距 3. The following reaction was done experimentally at various temperatures in order to obtain rate const

4、ants:O + HO2 OH + O2 T1 = 298 K k1 = 6.1 x 10-11 cm3 / molecule·sT1 = 229 K k2 = 7.57 x 10-11 cm3 / molecule·s(a) Using the experimental data, find the activation energy Eact.(b) Calculate the following thermodynamic properties at T = 298 K using transition state theory: E, H, S, G. 解：(a)

5、由Arrhenius公式 得： (1) (2) ： 則：（b）考慮恒溫恒壓過程:因其為氣相反應(yīng)，標(biāo)準(zhǔn)態(tài)通常選為1個(gè)大氣壓，故需據(jù)kc計(jì)算出kp： 據(jù)，得：或：由過渡態(tài)理論速率常數(shù)表達(dá)式： 得： 又：，因其為氣相反應(yīng)，標(biāo)準(zhǔn)態(tài)通常選為1個(gè)大氣壓，故：由得：4. The reaction of CH with N2 is of importance in the chemistry of planetary atmospheres and hydrocarbon flames. By understanding the basic reaction, other complex systems su

6、ch as combustion in the environment can be studied. The reaction is CH + N2 ( CHN2 ) HCN + N Using transition state theory, find the partition functions for each molecule and then the rate constant at 298 K. Also, specify all the degrees of freedom and the temperature dependence of the A factor. From experiment, the second-order rate constant at 298 K has been found to be kexp = 7.1 x 10-14 cm3 / molecule·s. Properties of the Transition State + Molecules CH N2 HCN2 ( assume linear adduct )M (amu = g / mol) 13.019 28.013 41.032I ( 10 -40 g c