物理化学期末考试试题

PHYSICAL CHEMISTRY

Final Exam

Academic Year 2007-2008 Semester 2 Examination Time 110minutes Test Subject Physical Chemistry of Higher Engineering Chemstry

Class Hours 40 Credits 2.5 Examination Form Close Book Total Score 100 Major & Grade Chemical engineering, Pharmaceutical engineering, Applied chemistry, Grade 06

Total Mark Percentage 70%

Remark This page is not a answer sheet, please write the answer on the mark card. Ⅰ MULTIPLE CHOICE (2 points for each question, total points: 24) 1. For the rate equation of the ozonolysis reaction 2O 3?→?

k

3O 2 is 2

3

3

O

2

O O d d 2

1p p k

t

p r =-=, the reaction is a (A )

(A ) first order reaction; (B) second order reaction; (C) unimolecular elementary reaction;

2. Which of the following conclusions for the two parallel reactions A is false ( b )

(A) k total = k 1 + k 2 (B ) E total = E 1 + E 2 (C) k 1 / k 2 = c X / c Y (D) t 1/2 = ln2 / (k 1 + k 2)

3. Which of the following statements about chain reaction is incorrect ( )

(A) the joint processes of chain reaction are chain-initiation, transitive and termination; (B) branched chain reaction may lead to an explosion under a certain condition;

(C) the rate of chain reaction can be treated by steady state approximation and equilibrium state approximation; (D) the rate of chain reaction is so fast that activation energy isn’t needed;

4. In the CaCl 2 solution with the concentration of 0.01mol?kg -1 at 298K, the mean ionic activity coefficient γ± of CaCl 2 is (d ) (remark: A=0.059)

(A) 0.847 (B) 0.791 (C) 0.889 (D ) 0.666

5. While the concentration of KCl solution increased form 0.01 mol·kg -1 to 0.1 mol·kg -1 at 298K, the conductivity κ and molar conductivity Λm would be ( )

(A) κ increased and Λm decreased; (B) κ increased and Λm increased; (C) κ decreased and Λm increased; (D) κ decreased and Λm are decreased.

6. The reaction O(l)H ),g (O ),g (H 222

1

2===+

Θ

Θ

p

p could be completed by combusting, the enthalpy variable is

)

1(m r H

?; if it is designed into a battery, the enthalpy variable is )

2(m r H

?.Maintaining the same T & P of the reactant and

product in the two conditions gave above, the relation of the two enthalpy variables is (c ) (A) )

1(m r H ?<)

2(m r H ? (B) )

1(m r H ?>)

2(m r H

? (C ) )1(m r H ?=)2(m r H

? (D) )

1(m r H

?= -)

2(m r H

?

7. For V 0360F e

F e

3./-=Θ

+

E ,V 771023

F e

F e

./=Θ

+

+

E , the Θ

+

F e

F e

2/E is ( c )

(A) 0.735V (B) 0.807V (C ) －0.44 V (D) －0.699 V

8. When the polarization occurs, the electrode potential on the two poles will change as the followe( b ) (A) E eq,anode ＞E anode ；E eq,cathod ＞E cathod (B ) E eq,anode ＜E anode ；E eq,cathod ＞E anthod (C) E eq,anode ＜E anode ；E eq,cathod ＜E cathod (D) E eq,anode ＞E anode ；E eq,cathod ＜E cathod

9. The relationship between surface tension and temperature of water is σ/N?m-1= 0.07364－4.95×10-6T, increase the unit surface area of water reversibly at pΘ, the minimum surface work consumption of the environment is (c )

(A) 4.95×10-6J?m-2(B) -4.95×10-6J?m-2

(C) 0.0722 J?m-2(D) -0.0722 J?m-2

10. For the concentration of the solute B in a solution is c B(surface) ＞c B(bulk phase)，so the ( b )

(A) dσ/d c＞0，ΓB＞0; (B) dσ/d c＜0，ΓB＞0;

(C) dσ/d c＜0，ΓB＜0; (D) dσ/d c＞0，ΓB＜0.

11. The Tyndall effect is ( a ) of colloidal particle to light.

(A) scattering effect, (B) reflection effect,

(C) refraction, (D) transmission effect.

12. Applied a DC electric field to the colloidal solution, the ( ) might do a directional movement to an electrode.

(A) colloid core; (B) colloidal; (C) micelle; (D) colse binder

ⅡBlank Filling (Total points:16)

1. (1 point)A reaction can be completed in a limited period of time and the reaction time is c

/k, the reaction order is .

2.（1 point）The equilibrium conversion of a reaction under certain condition is 25%, the reaction rate increased 3 times after adding an appropriate catalyzer, the equilibrium conversion is .

3. (2 pointts) The relation between the overall reaction coefficient and the elementary reaction confficients is k＝

2k2

2

1

3

1

?

?

?

?

?

?

k

k

,and the relation between the overall reaction apparent activation energy and each elementary apparent reaction

activation energy is E a＝.

4. (1 point) The resistances of 0.001mol ? dm-3and 0.01 mol ? dm-3 MA solution determined by the same conductivity cell are 25Ω and 2.5Ω respectively, then the molar conductivity ratio of the two solutions is .

5.(2 points) For the battery Pt,Cl2(pΘ)│Cl－(a Cl－=1)│Cl2(2pΘ),Pt,please give out the cell reaction .

6. (2 pointts) Definition of electrode polarization is

.

7. (2 points) In accordance with the difference of the intra molecular forces between solid-surface molecules and gas molecules, gas adsorption on solid surface can be divided into physical adsorption and chemical adsorption, the force of physical adsorption is

; the force of chemical adsorption is

.

8. (2 points) For the surface were flat, concave and convex of the same liquid, its equilibrium vapor pressure at T are respectively expressed as a p flat, p concave, p convex.The descending order of the equilibrium vapor pressures is > > .

9. (3 points) The AgI positive sol is synthesized though dropping a spot of KI dilute solution slowly into the dilute AgNO3 solution, the micelle structure is .If we add in K2SO4or CaCl2solution to get it coagulated, have the higher coagulation capacity.

Ⅲ (10 points)

For the overpotential of hydrogen on iron electrode is 0.350V and the activity of ferrous ion is 0.8 in the cathode region electrolyte, what is the minimum pH value for the solution while H2couldn't be released on the electrode during the electrolysis process? （Suppose the temperature is 298K, EΘ (Fe2+/Fe）= -0.440V）

Ⅳ (15 points)

The reaction D —→ P is a first order reaction, there was still 80% D left after the raction lasted 20minutes at 400K while it was 60% left after the reaction lasted 30minutes at 450K. What are the values of activation energy and the frequency factor for the first order reaction? What are the two half-life of D at each temperature?

Ⅴ (15points)

Design a cell, of which the reaction is as follows:

Fe2+(a1) + Ag+(a2) ==== Ag(s) + Fe3+(a3)

At 298K, EΘ(Fe3+/ Fe2+) = 0.77V, EΘ(Ag+/ Ag) = 0.7996V

(1) Please write out the cell expression and the electrode reactions;

(2) Calculate the standard electromotive force EΘ and the standard gibbs free energy change

△r G mΘ of the cell at 298K;

(3) Calculate the equilibrium constant K aΘ of the cell reaction at 298K.

Ⅵ (10 points)

The molar conductivities at infinite dilution of the following materials at 298K are given as follows：

Λm∞(HAc) = 390.72×10-4 S·m2·mol-1

Λm∞(NaAc) = 90.01×10-4 S·m2·mol-1

Λm∞(NaCl) = 126.45×10-4 S·m2·mol-1

The infinite dilute ionic mobility of Hydrogen ion is U∞(H+) = 36.2×10-8m2·s-1·V-1，Calculate the infinite dilute transference number of H+ in HCl solution.

Ⅶ (10 points)

Supersaturation phenomenon occurs when water vapor suddenly cold. In summer, salting clouds with granular dry ice dropped the temperature to 293K while the supersaturation of vapor(p/ps) is 4 at this point. At 293K, the surface tension of water is σ(H2O) = 72.75mN·m-1，ρ(H2O) = 997kg·m-3。

(1) The radius of the raindrops formed at the beginning

(2) The water molecular number in every raindrop.

Quarter Exam for Physical chemistry (II) – 3

2011-2012 Academic Year Fall Semester

PART 1 Choose the answer that best fit the statements. [Totally 30 points]

[1] Which activation does not depend on temperature.

(A) Arrhenius activation energy;

(B) Tolman activation energy;

(C) activation energy of transition state theory;

(D) activation energy of simple collision theory

[2] It is more possible for termolecular reaction to take in solution than in gaseous state, the main reason is

(A) diffusion is fast; (B) the polarity of solvent is high;

(C) cage effect; (D) the viscosity of solution is large

[3] Polyaniline can be used as light-emitting materials. Tow kinds of radiation can be sent out by polyaniline: fluorescence and phosphorescence, the wavelength of them are denoted as λF and λP, then ：

(A) λF > λP; (B) λF < λP, (C) λF = λP (D) uncertain.

[4] The activation energy of which reactions has definite physical meaning:

(A) H2 + I2 == HI;

(B) 2I + H2 == 2HI

(C) C12H22O11 + H2O == C6H12O6 + C6H12O6

(D) Pb(C2H5)4 == Pb + 4C2H5

[5] Which of the following theories can explain the effect of temperature on activation energy?

(A) simple collision theory

(B) transition state theory

(C) RRKM theory for unimolecular reaction

(D) none of them.

PART II Fill in the blanks 【Totally 30 points】

[1] The rate law for the reaction Cl2(g) + CHCl3(g) → HCl(g) + CCl4 is r = k[Cl2]1/2[CHCl3], the units for

k is _________ assuming time in second.

[2] For consecutive reaction A B C, E a,1> E a,2; A1> A2, if we want to obtain more B as product,

should we make the reaction take place at _____________ (higher or lower) temperature.

[3] For reaction mechanism A B C, use k1, k2, and k3to show at what conditions

can we use steady-state approximation to treat intermediate B. ______________.

[4] For the following mechanism, the change rate of [C] can be expressed as ____

2A + B C, C + D E, 2C F

[5] The frequency of the light valid for activation of Br2 to initiate reaction is ______. ?H m(Br-Br)

= 193 kJ/mol.

PART III (totally 16 points)

[1] The following plot is the energy surface of reaction

A → C

A → D

(1) Indicate the transition states (saddle point) of the two

reactions and the reaction coordinate via transition state to C

and D on the plot.

(2) Estimate which activation energy of the two reactions is

higher, and which of the product is the main product.

(3) If we want to obtain more main product, should we conduct the

reaction at higher or lower temperature?

[2] The mechanism of reaction 2ICl + H2→ 2HCl + I2 was proposed to be

(1) H2 + ICl → HCl + HI

(2) ICl + HI → HCl + I2

The bond enthalpy ?H m(H-H) = 436 kJ/mol, ?H m(I-Cl) = 211 kJ/mol, ?H m(I-H) = 298 kJ/mol, ?H m(H-Cl) = 432 kJ/mol, ?H m(I-I) = 151 kJ/mol.

Please determine which step is the rational r.d.s., deduced the rate law of the reaction according to this mechanism.

PART IV Calculations (totally 24 points)

[1] The activation energy of an enzyme-catalyzed reaction occurring in humane body is 51.0 kJ/mol, the normal temperature of human is 36.8 o C. When the man gets fever and his temperature rises to 39.5 o C. Calculate the increase percentage of catalysis rate.

[2] NO2, main pollutant from car exhaust, can induce formation of O3 at low air and make photochemical fog by the following mechanism:

(1) NO2→ NO + O (k = 6.0?10-3 s-1 )

(2) O + O2→ O3 (k = 1.0?106 mol-1 dm3 s-1)

When the concentration of NO2 is 3.0?10-8 mol/dm3, calculate the formation rate of O3.