化學反應動力學六、七、九章答案(共6頁)

1、精選優(yōu)質文檔-傾情為你奉上化學反應動力學第六、七、九章習題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）反應截面與反應速率常數的關系為： k(u) =R u R 其中，u R：相對平動速率解法1：因反應截面為常數，故可先求出平均速率，然后據k(T) =R <u R>求k(T) 根據氣體分子運動論： 其中：Maxwell-Boltzmann分布函數 ：折合質量。 則有：k(T) =R<u R>解法2： (b) Arrhenius公式為：，k與T呈指數關系，隨T的增加，k呈指數增長。而(a) k(T)T1/2 ,(b) ,與Arrhenius公式中k與T的關系不同。2. For a Lennard-Jone

3、s “ 6 - 12 ” potential determine the internuclear distance at the potential energy minimum. 解：Lennard-Jones 勢能函數為： 其中：Lennard-Jones 勢能函數的勢阱深度 r ：分子間距離 ：V(r)=0, r時的r值。 則： 當時，勢能V為最小值， 得： 即，勢能最小時，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，標準態(tài)通常選為1個大氣壓，故需據kc計算出kp： 據，得：或：由過渡態(tài)理論速率常數表達式： 得： 又：，因其為氣相反應，標準態(tài)通常選為1個大氣壓，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