Shandong University Physical Chemistry(2)Quarter Exam-1 2020-2021 Aoadommio Year Fall Semester 号国國五六[七九团十分分人 (A)H2+l2-2HI is an elementary reaction, (B)H+1→→2 HI is a complex reaction; 2020-2021 Academic Year. Fall Semester C)H2+I2-2HI is a bimolecular reaction The First Quarter Exam of Physical Chemistry(2) (D) The partial order ofHz is I [1-5] For branched chain explosion, there are three explosion limits, Pl, P, and p. For pi, All constants can be found in Yin Y J, Physical Chemistry, P. 438 ) The collision of radical with container well increases 舞兽人 (C) The thermal conductivity is higher at more dense state; 2 L. Choose the best answer for the following questions using a cirele(4 points for(D) The gaseous terminating is dominant. each question, totally 24 points) [I-6] Among the following photophysical process, which can send out fluorescence [l-l For an exothermal reaction, its equilibrium yield is 25% at 400 K. When a catalyst is (A) S2-S1 internal conversion; (B)SHTI intersystem crossing, Introduced, the equilibrium can be achieved in the same time at 300 K. Then the equilibrium (C)Sr So decay? yield will be (A) Higher than 25%,(B)less than 25 舞分|舞卷人 封 (C)Equal to 25%, (D)uncertain. [1-2]For the following statements of rate constant, which is nor correct? IL. Fill the blanks with the best answers(4 points for each blank, totally (A) Rate constant is the proportional factor in rate law, (B) Rate constant depends on temperature and pressure [2-1A reaction takes place according to the following mechanism: (C) For reaction with different reaction order, the unit of rate constant is different A+B一C+D (D) Rate constant is independent of concentration of reactants 2C- F [l-3] For following reactions, the activation energy of which reaction is the second highest? F+B一2A+G Given that DH-H 436 k mol-: DcuP 243 kJ mol-l, DH-cF 431 W mol-l Then the stoichiometric equation of the overall reaction is 3B-2D+ G (A)CHCI-, 2C1;(243 kJ mol-l Substance A is catal B)C14+HH→→HC1+H(26.55 k mol-) lyst C)H+CkCI-+H-Cl+Cl; (12.15 kJ mol-l [2-2For reaction 21-+ H:02-12+H:O, its experimental rate law is (D)2C1+M-Cl+M(0 k mol-l 4H2o2 JIH,O [1-4] The experimental rate law of H2+12- 2HI is r= AHJ[]. Based on this experimental fact, what conclusion can we get The mechanism is suggested to be composed of two step. Which step is the 第1页共2
2020-2021 Academic Year Fall Semester 题号 一 二 三 四 五 六 七 八 九 十 总分 总分人 得分 2020-2021 Academic Year, Fall Semester The First Quarter Exam of Physical Chemistry (2) ---------------------------------------------------------------------------------------------- All constants can be found in Yin Y. J., Physical Chemistry, p. 438 得分 阅卷人 I. Choose the best answer for the following questions using a circle (4 points for each question, totally 24 points) [1-1] For an exothermal reaction, its equilibrium yield is 25% at 400 K. When a catalyst is introduced, the equilibrium can be achieved in the same time at 300 K. Then the equilibrium yield will be (A) Higher than 25%; (B) less than 25%; (C) Equal to 25%; (D) uncertain. [1-2] For the following statements of rate constant, which is not correct? (A) Rate constant is the proportional factor in rate law; (B) Rate constant depends on temperature and pressure; (C) For reaction with different reaction order, the unit of rate constant is different; (D) Rate constant is independent of concentration of reactants. [1-3] For following reactions, the activation energy of which reaction is the second highest? Given that DH—H= 436 kJ mol-1；DCl—Cl= 243 kJ mol-1 , DH—Cl= 431 kJ mol-1 . (A) Cl⎯Cl ⎯→ 2Cl; (243 kJ mol-1 ) (B) Cl + H⎯H ⎯→ H⎯Cl + H;(26.55 kJ mol-1 ) (C) H + Cl⎯Cl ⎯→ H⎯Cl + Cl; (12.15 kJ mol-1 ) (D) 2Cl + M ⎯→ Cl2 + M. (0 kJ mol-1 ) [1-4] The experimental rate law of H2 + I2 ⎯→ 2HI is r = k[H2][I2]. Based on this experimental fact, what conclusion can we get? (A) H2 + I2 ⎯→ 2HI is an elementary reaction; (B) H2 + I2 ⎯→ 2HI is a complex reaction; (C) H2 + I2 ⎯→ 2HI is a bimolecular reaction; (D) The partial order of H2 is 1. [1-5] For branched chain explosion, there are three explosion limits, p1, p2, and p3. For p2, which of the following statements is correct? (A) The collision of radical with container well increases; (B) It can be due to some impurity; (C) The thermal conductivity is higher at more dense state; (D) The gaseous terminating is dominant. [1-6] Among the following photophysical process, which can send out fluorescence (A) S2⎯→S1 internal conversion; (B) S1⎯→T1 intersystem crossing; (C) S1⎯→S0 decay; (D) T1⎯→S0 decay. 得分 阅卷人 II. Fill the blanks with the best answers (4 points for each blank, totally 24 points) [2-1] A reaction takes place according to the following mechanism: A + B C + D 2C F F + B 2A + G ⎯⎯→ ⎯⎯→ ⎯⎯→ Then the stoichiometric equation of the overall reaction is _3B⎯→2D + G ________. Substance A is ____catalyst_____________. [2-2] For reaction 2I− + H2O2⎯→I2 + H2O, its experimental rate law is 2 2 2 2 [H O ] - = [I ][H O ] d k dt − The mechanism is suggested to be composed of two step. Which step is the Shandong University Physical Chemistry (2) Quarter Exam-1 College Major Grade Student No. Name … … … … … … … … … … … … … … 密 … … … … … … … … … … 封 … … … … … … … … … … 线 … … … … … … … … … … … … … 第 1 页 共 2 页
Shandong University Physical Chemistry(2)Quarter Exam-l 2020-2021 Academic Year Fall Semester rate-determining step, (I)or(2) (4)[2 points) If the absorbance intensity of incident light is la. Find the rate law of step (a) (1)1-+HO21O-+H2O of mechanism (2) rakI lal (5)8 points) Deduce the rate law from mechanism(2). (2 2-3]The quantum yield of Hz+ Clz reaction(a) initiated by light radiation in gaseous phase is about 1010. When this reaction is performed in CHCls solution with quantum (6)[2 points] What is the reaction order of the reaction? [first-order yield of dn, then o)_>_oe. and Hx+l2- performed at the same higher temperature, give (1)(a)C2+h→C2 (b)C2Cl4+C2→→C2C4 explanation to their reaction rate based on SCT and TST theories. [The covalent radius and a)Cl2+by-→2C Cl are 99.4 pm and 35.45, for I, they are 133 pm and 126.90, Bond energy (bcC14+C-→C2C of CkCl, I, H-Cl and H is 243, 151, 431, 298 kJ mo (cC1,Cl2-→C2C2+C (d)c,Cl,+C2Cls-CICl+C:CL Ead It was found that the quantum yield of the reaction is rather high, Answer the following The collision diameter of Hx+l is larger than that of Hx+CI, the translational velocity of 0 Which mechanism is correct [(2) is corn单mw单 Cl is higher than that of Iz. But the difference resulted in by different collision yield of(I)is 1-2 points and translational velocity is not obvious. However, the activation energy of reaction (2)[3 points) For mechanism (2), define the initiating (a), propagating (b'c) and Hz+CIy is much less than that of Hz+l-. therefore, the rate of Hx+h- reaction is terminating (d)step much higher. [This is not the casel (3)[2 points) In order to initiate the reaction, what kind of light irradiation(wavelength in For TST the interaction between CI--H--H is much stronger than that between I--H---H, which benefits the break of HH bond and initiates the subsequent chain nm) is required? Given that bond dissociation energy of Cl-Cl bond: DaCI=243 k mo.492.3mm 第2页共2页
2020-2021 Academic Year Fall Semester rate-determining step, (1) or (2)?____(1)__ (1) I − + H2O2⎯→IO− + H2O (2) 2H 2 2 IO I I H O + − − + ⎯⎯⎯→ + [2-3] The quantum yield of H2 + Cl2 reaction (1) initiated by light radiation in gaseous phase is about 10 4~106 . When this reaction is performed in CHCl3 solution with quantum yield of 2, then 1__>__1 (>, <, =). This change in quantum yield can be ascribed to the __solvent cage____ effect. [2-4] An organic compound can be formed biologically after absorbance of 8 photon with wavelength of 600 nm. The combustion enthalpy of this compound is 468.6 kJ mol-1 . Then the energy efficiency is __468.6/1595.0 = 29.38%______. 得分 阅卷人 III. Answer the following questions: (Totally 30 points) [3-1] For reaction addition reaction C2Cl4 + Cl2 ⎯→ C2Cl6, two mechanisms are proposed. (1) 1 2 * 2 2 * 2 4 2 2 6 (a) Cl Cl (b) C Cl Cl C Cl k k + ⎯⎯→ h + ⎯⎯→ (2) ' 1 ' 2 ' 3 ' 4 2 ,1 2 4 2 5 ,2 2 5 2 2 6 ,3 2 5 2 5 2 6 2 4 ,4 (a') Cl 2Cl (b') C Cl Cl C Cl (c')C Cl Cl C Cl Cl (d')C Cl C Cl C Cl C Cl k a k a k a k a h E E E E + ⎯⎯→ + ⎯⎯→ + ⎯⎯→ + + ⎯⎯→ + It was found that the quantum yield of the reaction is rather high. Answer the following questions: (1) [4 points] Which mechanism is correct【(2) is correct—2points】? Why? [the quantum yield of (1) is 1—2 points. ] (2) [3 points] For mechanism (2), define the initiating (a’), propagating (b’c’) and terminating (d’) step. (3) [2 points] In order to initiate the reaction, what kind of light irradiation (wavelength in nm) is required? Given that bond dissociation energy of Cl—Cl bond: DCl-Cl = 243 kJ mol-1 . [492.3 nm] (4) [2 points] If the absorbance intensity of incident light is Ia. Find the rate law of step (a’) of mechanism (2); [r=k1’Ia] (5) [8 points] Deduce the rate law from mechanism (2). ' 2 6 1 ' ' 3 2 4 1 d[C Cl ] [Cl ] d 2 a a k k I k k I t − = + (6) [2 points] What is the reaction order of the reaction? [first-order] (7) [2 points] Give the relation between the apparent activation energy and those of the relevant elementary steps. 1 , 3 2 a app E E E = + =133.6 kJ mol-1 [3-2] Based the rate law of simple collision theory, answer the following questions: (1) [3 points] List as many as possible the ways to increase the fraction of activated molecules. (1) increase temperature; (2) use suitable catalyst; (3) choose suitable solvents. (2) [4 points] For H2+Cl2⎯→ and H2+I2→ performed at the same higher temperature, give explanation to their reaction rate based on SCT and TST theories. [The covalent radius and atomic mass of Cl are 99.4 pm and 35.45, for I, they are 133 pm and 126.90; Bond energy of Cl⎯Cl, I⎯I, H⎯Cl and H⎯I is 243, 151, 431, 298 kJ mol-1 ] 2 AB 8 exp RT E c r d L RT = − The collision diameter of H2+I2 is larger than that of H2+Cl2, the translational velocity of Cl2 is higher than that of I2. But the difference resulted in by different collision diameter and translational velocity is not obvious. However, the activation energy of reaction H2+Cl2⎯→ is much less than that of H2+I2→, therefore, the rate of H2+I2→ reaction is much higher. [This is not the case!] For TST, the interaction between Cl---H---H is much stronger than that between I---H---H, which benefits the break of H⎯H bond and initiates the subsequent chain reaction. Shandong University Physical Chemistry (2) Quarter Exam-1 学院 专业 级 学号 姓名 … … … … … … … … … … … … … … 密 … … … … … … … … … … 封 … … … … … … … … … … 线 … … … … … … … … … … … … … 第 2 页 共 2 页
Shandong University Physical Chemistry(2)Quarter Exam-1 2020-2021 Academic Year Fall Semester 得分■人 [4-2 For competing reaction A+B→5→C I. Calculation( totally 22 points): 41[3 points] Saponification(皂化) reaction This reaction order of A and B is first-order. At 300 K, when the initial concentration of A CH COOC:Hs+ NaoH- CH: COONa +C:HsOH and B is I mol dm after 30 min of reaction, 15% A converts to C and 25%A converts to is a second-order reaction. If the initial concentrat CH: COOCzHs and NaOH is 0.010 mol dm, after 600 s, 39.0% CH: COOC2Hs is converted at 298.2 K. At 308. 2K, after 600 s, D) Calculate the ratio of hi/k2; 0.6 (2) Determine kiand kz; k1=0.0083, h 55% CHECOOC2Hs is converted 密 (3) The activation energy of reaction(I)and (2)is Eal- 150 W mor and Ea?=140 U (s points What is the activation energy of this reaction mol-l, respectively. What is the apparent activation energy of the overall reaction? on S=k,k=0. 1066 dm molr-sl, k:0.2037 dm'mol-s [140 W mol-1 (4)If we want to increase the yield of C, should we carry the reaction at higher or lower 4m4点“4948m emperature? [higher (2)(4 points]At 288.2 K, how many CHsCOOCzHs can be converted after reaction of 600 s? 封 k=0.0533 dm' mol-I s-I conversion.24% 3)14 points) If we want to convert 50% CHsCOOCiHs at 288.2 K, how many time is needed? 18762s 第4页 4
2020-2021 Academic Year Fall Semester 得分 阅卷人 IV. Calculation (totally 22 points): [4-1] [13 points] Saponification (皂化) reaction: CH3COOC2H5 + NaOH ⎯→ CH3COONa + C2H5OH is a second-order reaction. If the initial concentration of CH3COOC2H5 and NaOH is 0.010 mol dm-3 , after 600 s, 39.0% CH3COOC2H5 is converted at 298.2 K. At 308.2 K, after 600 s, 55% CH3COOC2H5 is converted. (1) [5 points] What is the activation energy of this reaction? 0 1 1 kt c c − = , k1=0.1066 dm3 mol-1 s -1 ; k2=0.2037 dm3 mol-1 s -1 ; ln ln - E a k A RT = ;Ea = 49.48 kJ mol-1 (2) [4 points]At 288.2 K, how many CH3COOC2H5 can be converted after reaction of 600 s? k=0.0533 dm3 mol-1 s -1 conversion=24.24%. (3) [4 points] If we want to convert 50% CH3COOC2H5 at 288.2 K, how many time is needed? 1876.2 s [4-2] For competing reaction 1 2 (1) A+B C (2)A+B D k k ⎯⎯→ ⎯⎯→ This reaction order of A and B is first-order. At 300 K, when the initial concentration of A and B is 1 mol dm-3 , after 30 min of reaction, 15% A converts to C and 25% A converts to D. (1) Calculate the ratio of k1/k2; 0.6 (2) Determine k1and k2; [k1=0.0083, k2=0.014] (3) The activation energy of reaction (1) and (2) is Ea,1 = 150 kJ mol-1 and Ea,2 = 140 kJ mol-1 , respectively. What is the apparent activation energy of the overall reaction? [140 kJ mol-1 ] (4) If we want to increase the yield of C, should we carry the reaction at higher or lower temperature? [higher] Shandong University Physical Chemistry (2) Quarter Exam-1 学院 专业 级 学号 姓名 … … … … … … … … … … … … … … 密 … … … … … … … … … … 封 … … … … … … … … … … 线 … … … … … … … … … … … … … 第 4 页 共 4 页 _________________________