Name:______________________________

Part A: Multiple Choice

Value: 42 marks Suggested Time: 60 minutes

1. Consider the reaction:Ca(s) + 2H2O(l) Ca(OH)2(aq) + H2(g)

At a certain temperature, 2.50 g Ca reacts completely in 30.0 seconds. The rate of consumption of Ca is

A. 0.00208 mol / minB. 0.0833 mol / minC. 0.125 mol / minD. 5.00 mol / min

2. The minimum amount of energy required to overcome the energy barrier in a chemical reaction is the

A. heat of reaction.B. activation energy.C. KE of the reactants.D. enthalpy of the products.

3. An activated complex is a chemical species that isA. stable and has low PE.B. stable and has high PE.C. unstable and has low PE.D. unstable and has high PE.

4. Consider the following reaction mechanism:Step 1: 2NO + H2 N2 + H2O2 Step 2: H2O2 + H2 2H2O

In this reaction, H2 is aA. product.B. catalyst.C. reactant.D. reaction intermediate.

Chemical Kinetics Exam

INSTRUCTIONS: For each question, select the best answer and record your choice on the Response Form provided. Using an HB pencil, completely fill in the circle that has the letter corresponding to your answer.

5. A certain reaction is able to proceed by various mechanisms. Each mechanism has a different Ea and results in a different overall rate. Which of the following best describes the relationship between the Ea values and the rates?

6. Consider the following PE diagram:

The forward reaction can be described as

H Activation Type of(kJ) Energy (kJ) Reaction

A. + 20 80 endothermic B. + 20 60 exothermic C. - 20 80 exothermic D. - 20 100 endothermic

7. The slowest of the following reactions isA. Ag(aq)

+ + Cl-(aq) AgCl(s)

B. H3O+(aq) + OH-

(aq) 2H2O(l

C. 3Ba2+(aq) + 2PO4

3-(aq) Ba3(PO4)2(s)

D. Cu(s) + 2Ag+(aq) Cu2+

(aq) + 2Ag(s)

8. The rate of a chemical reaction is equal to the slope of a graph with the axes labelled

x-axis y-axisA. time rateB. mass timeC. volume of gas timeD. time concentration

9. Consider the following reaction:CH4(g) + 2O2(g) CO2(g) + 2H2O(g) + heat

The diagram which represents the relationship between rate and temperature is:

10. Which of the following describes the energy of colliding particles as reacting molecules approach each other?

KE PE A. decreases increases B. increases decreases C. decreases remains constant D. remains constant increases

11. The average kinetic energy of colliding particles can be increased byA. adding a catalyst.B. increasing pressure.C. increasing temperature.D. increasing reactant concentration.

12. A substance that increases the rate of a chemical reaction and may be recovered unchanged at the end of the reaction is a(n)

A. product.B. catalyst.C. activated complex.D. reaction intermediate.

13. Consider the following PE diagram for a reversible reaction:

Which of the following describes this reaction?

Direction Activation HEnergy (kJ) (kJ)

A. reverse 30 - 10 B. forward 40 - 10 C. forward 30 + 10 D. reverse 40 + 10

14. Which of the following can be used to represent the rate of a reaction?

A. g / LB. g / molC. (g · min) / molD. M / min

15. Consider the following reaction:2H2O2(l) 2H2O(l) + O2(g)

Which graph shows the relationship between rate of consumption of H2O2 and time?

16. Consider the following reaction:Mg(s) + 2HCl(aq) H2(g) + MgCl2(aq)

The rate of this reaction increases when more magnesium is added. This change is caused by the

A. addition of a catalyst.B. increase in surface area.C. change in nature of the reactants.D. increase in concentration of reactants.

17. A catalyst changes the rate of a reaction byA. changing H.B. increasing the temperature.C. decreasing the energy of the products.D. providing an alternate reaction mechanism.

18. Which graph shows the relationship between activation energy (Ea) and temperature?

19. Consider the following reaction:CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

At a certain temperature, 1.0 mol CH4 is consumed in 4.0 minutes. The rate of production of H2O isA. 0.25 mol / minB. 0.50 mol / minC. 2.0 mol / minD. 8.0 mol / min

20. The changes in PE and KE, as reactant molecules approach each other, can be represented by

21. Consider the following PE diagram:

Which of the following describes this reaction?

H Activation Reaction(kJ) Energy (kJ)

A. - 20 40 catalyzed B. - 20 60 catalyzed C. + 20 40 uncatalyzed D. + 20 60 uncatalyzed

22. A chemical reaction that gives off energy isA. exothermic and H is positive.B. exothermic and H is negative.C. endothermic and H is positive.D. endothermic and H is negative.

23. Consider the following reaction involving 1.0 g of powdered zinc:Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

Trial Temperature Concentration

(C) of HCl (M)

1 40 3.0

2 20 3.0

3 40 6.0

The rates, in order of fastest to slowest, areA. 1, 2, 3B. 2, 1, 3C. 3, 1, 2D. 3, 2, 1

24. Activation energy can be described as theA. energy of motion.B. energy of the activated complex.C. energy difference between the reactants and the products.D. energy difference between the reactants and the activated complex.

25. Increasing the temperature of a reaction increases the reaction rate byI. increasing frequency of collisionsII. increasing the kinetic energy of collisionIII. decreasing the potential energy of collision

A. I only.B. I and II only.C. II and III only.D. I, II and III.

26. Consider the graph for the following reaction:CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O(l)

The average rate of reaction is greatest in the time intervalA. 0 - 1 minute.B. 0 - 2 minutes.C. 0 - 3 minutes.D. 0 - 4 minutes.

27. Consider the following mechanism for a reaction:Step 1: HBr + O2 HOOBrStep 2: HBr + HOOBr 2HOBr Step 3: 2HOBr + 2HBr 2Br2 + 2H2O

Which of the following statements is correct?A. Br2 is a reactant.B. HBr is a product.C. HOBr is a catalyst.D. HOOBr is a reaction intermediate.

28. Consider the following reaction:Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

A graph of concentration of HCl vs time could be represented by

29. Consider the following experiments, each involving equal masses of zinc and 10.0 mL of acid:

The rate of reaction in order from fastest to slowest isA. I > II > III B. II > I > III C. III > I > II D. III > II > I

31. Consider the following reaction mechanism:Step 1: ClO- + H2O HClO + OH-

Step 2: I- + HClO HIO + Cl-

Step 3: HIO + OH- IO- + H2O

The catalyst isA. IO- B. H2O C. ClO- D. HClO

32. The rate-determining step in a reaction mechanism is always theA. last step.B. first step.C. fastest step.D. slowest step

33. The addition of a catalyst to an exothermic reaction increases the rate of the reaction because it decreases theA. HB. activation energyC. H and the activation energyD. activation energy and the amount of energy released.

Use the following potential energy diagram to answer question 34.

34. The above energy diagram represents a four step reaction mechanism. Which is the rate determining step?A. 1B. 2C. 3D. 4

35. Consider the following two-step reaction mechanism:Step 1: NO + NO3 (slow)Step 2: NO3 CO NO2 CO2 (fast)

Which one of the following changes would result in the greatest increase in reaction rate?A. increase [CO]B. decrease [NO]C. increase [NO2]D. decrease [NO3]

36. Which of the following factors affects the rate of heterogeneous reactions ONLY?A. Presence of a catalyst.B. Temperature of the reactants.C. Surface area of reactants.D. Concentration of reactants.

37. Consider the following reaction:CaCO3(s) + 2HCl(aq) CO2(g) + CaCl2(aq) + H2O(l) + heat

In which of the following will BOTH of the described procedures cause an increase in the rate at which products are formed?A. Increase [HCl] and decrease pressure.B. Increase [HCl] and increase temperature.C. Increase [HCl] and decrease temperature.D. Grind up the CaCO3 and decrease temperature.

38. The following equation represents the reaction between copper metal and aqueous silver nitrate solution:

Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

brown colorless blue greysolid solution solution solid

Which of the following properties would BEST monitor the rate of this reaction?A. Concentration of NO3

-(aq)

B. Gas pressure.C. Color of the solution.D. Mass of the system.

39. Dust particles suspended in the air inside unheated grain elevators can sometimes

react explosively because the dust particles have aA. high kinetic energy.B. high activation energy.C. catalytic effect on the reaction.

D. large surface area for the reaction.40. Consider the following collisions, each occurring at the same temperature:

Which one of the following factors explains why collision one is successful while collision two is not successful?A. Catalyst.B. Geometry.C. Concentration.D. Kinetic energy.

Use the following diagram to answer questions 41 and 42.

41. Select the true statement concerning the above potential energy diagram.

A. The catalyzed reaction has a larger H.B. The uncatalyzed reaction has a larger H.C. The catalyzed reaction has a greater rate of reaction.D. The uncatalyzed reaction has a greater rate of reaction.

42. Which point on the diagram above represents the potential energy of the activated

complex formed in the uncatalyzed reaction?A. IB. IIC. IIID. IV

43. The class that you attend every Tuesday and Thursday from 6:45 to 9:45 pm and wouldn’t miss for the world (even on Halloween and Christmas) isA. Trick or Treating 12B. Santa 12C. Chemistry 12D. Bite Me 12

44. The instructor for this course isA. The GrinchB. Jack O. LanternC. Mr. ChoyD. Easter Bunny

Part B: Written Response

Value: 26 marks Suggested Time: 40 minutes

1. Consider the following reaction mechanism:

Step 1 ?Step 2 H2 + Cl HCl + HStep 3 H + Cl2 HCl + ClStep 4 Cl + Cl Cl2

Overall H2 + Cl2 2HCl

a) Write the equation for Step 1. (2 marks)

INSTRUCTIONS: You will be expected to communicate your knowledge and understanding of chemical principles in a clear and logical manner. Your steps and assumptions leading to a solution must be written in the spaces below the questions. Answers must include units where appropriate and be given to the correct number of significant figures. For questions involving calculation, full marks will NOT be given for providing only an answer.

b) Define the term “reaction intermediate” and identify the reaction intermediate(s) in the above reaction mechansim. (2 marks)

2. An experiment is done to determine the rate of the following reaction:

2Al(s) + 6HCl(aq) 3H2(g) + 2AlCl3(aq)

a) Calculate the rate of formation of H2 in mol/min.(2 marks)

b) Calculate the rate of consumption of Al in g/sec.(2 marks)

3. Consider the following reaction:CaCO3(s) + 2H+

(aq) Ca2+(aq) + H2O(l) + CO2(g)

a) List four factors that would increase the rate of the above reaction. (4 marks)i.

ii.

iii.

iv.

b) Using collision theory, explain how each of these four factors increase the rate of the reaction.

(4 marks)i.

ii.

iii.

iv.

4. Consider this reaction: MgCO3(s) + 2HCl(aq) MgCl2(aq) + H2O(l) + CO2(g)

Suggest two properties which could be used to determine the rate of this reaction, and state what would happen to each property as the reaction proceeds. (4 marks)i.

ii.

5. Describe the relationship between activation energy and the rate of a chemical reaction.

(2 marks)

6. Consider the following potential energy diagram for a reversible reaction:

a) Calculate the activation energy for the forward reaction. (1 mark)

b) Calculate H for the forward reaction. (1 mark)

c) Calculate the activation energy for the reverse reaction. (1 mark)

d) On the diagram above, sketch a curve that could result when a catalyst is added.

(1 mark)

Part C: Bonus Question

1. Consider the following KE distribution curve for colliding

particles:

a) On the diagram above, sketch a line for the distribution of collisions at a higher temperature. (2 marks)

b) Shade in the area representing the collisions that could result in forming an activated complex at the lower temperature. (1 mark)