Chapter 17-18 Practice Test

Name: ________________________ Class: ___________________ Date: __________

ID: A

Chapter 17-18 Practice Test

Multiple Choice Identify the choice that best completes the statement or answers the question.

____ 1. Examining a chemical system before and after a reaction reveals the

a. net chemical change.

c. intermediates.

b. reaction mechanism.

d. activated complex.

____ 2. In the reaction represented by the following equation, a possible intermediate is H2(g) + I2(g) 2HI(g)

a. H2.

c. H2I.

b. HI.

d. I2.

____ 3. Reactions whose reactants and products exist in a single phase are called

a. reaction mechanisms.

c. homogeneous reactions.

b. heterogeneous reactions.

d. activated complexes.

____

4. What is the overall equation for the formation of hydrogen iodide from its elements? a. H(g) + I(g) HI(g) b. H 2 (g) + I 2 (g) 2HI(g) c. H(g) + I 2 (g) HI(g) + I(g) d. H2 (g) + I(g) HI(g) + H(g)

____ 5. To react, gas particles must a. be in the same physical state. b. have the same energy.

c. have different energies. d. collide.

____

6. If colliding molecules have an orientation that favors reaction, they have a. the correct angles and distances between atoms. b. sufficient energy for each molecule. c. speeds that are neither too fast nor too slow. d. entropy values in the proper range.

____ 7. Which attempts to explain chemical reactions and physical interactions of molecules?

a. chemical kinetics

c. thermodynamics

b. collision theory

d. thermochemistry

____

8. If a collision between molecules is very gentle, the molecules are a. more likely to be favorably oriented. b. less likely to be favorably oriented. c. more likely to react. d. more likely to rebound without reacting.

____ 9. A short-lived structure formed during a collision is a(n)

a. reagent.

c. activated complex.

b. catalyst.

d. inhibitor.

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Name: ________________________

ID: A

____ 10. How does the energy of the activated complex compare with the energies of reactants and products? a. It is lower than the energy of both reactants and products. b. It is lower than the energy of reactants but higher than the energy of products. c. It is higher than the energy of reactants but lower than the energy of products. d. It is higher than the energy of both reactants and products.

____ 11. Activation energy is a. the energy required to form the activated complex. b. the net energy required to turn reactants into products. c. the enthalpy of reaction. d. free energy.

____ 12. In an energy-profile graph, the activated complex is represented at the

a. left end of the curve.

c. bottom of the curve.

b. right end of the curve.

d. top of the curve.

____ 13. In a diagram of an activated complex, broken lines represent

a. actual bonds.

c. electrons.

b. partial bonds.

d. bond energies.

____ 14. Raising the temperature of reactants in a system a. increases the average kinetic energy of the molecules. b. decreases the average kinetic energy of the molecules. c. decreases the rate of collision of molecules. d. has no effect on the average kinetic energy of molecules.

____ 15. Raising the temperature of reactants in a system a. increases the average molecular motion. b. decreases the average molecular motion. c. has no effect on the average molecular motion. d. disturbs the system so that the collision theory no longer applies.

____ 16. If a collision between molecules is oriented properly, the molecules are

a. more likely to react.

c. less likely to form an intermediate.

b. more likely to rebound without

d. less likely to react.

interacting.

____ 17. The energy change, E, for a reaction is the energy difference between the

a. product and the intermediate.

c. product and the activated complex.

b. product and the reactant.

d. reactant and the intermediate.

____ 18. The activation energy for a reaction is the energy difference between the

a. product and the intermediate.

c. reactant and the activated complex.

b. product and the reactant.

d. reactant and the intermediate.

____ 19. Which of the following is true in an endothermic reaction? a. energy of products < activation energy < energy of reactants b. energy of reactants < activation energy < energy of products c. energy of products < energy of reactants < activation energy d. energy of reactants < energy of products < activation energy

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Name: ________________________

ID: A

____ 20. Which of the following is true in an exothermic reaction? a. energy of products < activation energy < energy of reactants b. energy of reactants < activation energy < energy of products c. energy of products < energy of reactants < activation energy d. energy of reactants < energy of products < activation energy

____ 21. Which branch of chemistry studies reaction rates?

a. thermochemistry

c. chemical kinetics

b. thermodynamics

d. calorimetry

____ 22. Which branch of chemistry studies reaction mechanisms?

a. thermochemistry

c. chemical kinetics

b. thermodynamics

d. calorimetry

____ 23. The usual condition for reaction, a favorable orientation, is not necessary for

a. synthesis reactions.

c. single-displacement reactions.

b. decomposition reactions.

d. double-displacement reactions.

____ 24. Chemical kinetics studies a. the factors that affect the rate of reaction. b. the mathematical expressions for the rate of reaction. c. the factors that affect the rate of reaction and the mathematical expressions for the rate of reaction. d. the effect of quantum kinetics on chemical reactions.

____ 25. How fast something changes with time is a(n)

a. area.

c. order.

b. rate.

d. collision.

____ 26. Reaction rate depends upon a. both collision frequency and efficiency. b. average kinetic energy. c. collision efficiency. d. average potential energy.

____ 27. The decrease in reactant concentration per unit time in a reaction is a measure of the

a. reaction rate.

c. overall reaction.

b. heterogeneous reaction.

d. reaction mechanism.

____ 28. Which substance naturally combines most rapidly with oxygen?

a. platinum

c. iron

b. sodium

d. coal

____ 29. If the surface area of reactants is larger, a. the reaction rate is generally higher. b. the reaction rate is generally lower.

c. the reaction rate is not affected. d. the rate-determining step is eliminated.

____ 30. In heterogeneous reactions, the reactants a. have unequal masses. b. are not equally reactive.

c. have unequal volumes. d. are in different phases.

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Name: ________________________

ID: A

____ 31. Changing the pressure of a gas is another way of changing its

a. temperature.

c. surface area.

b. concentration.

d. composition.

____ 32. Which process is used to speed up chemical reactions?

a. calorimetry

c. activation

b. catalysis

d. inhibition

____ 33. Which term describes a catalyst in the same phase as the reactants and products?

a. homogenous

c. activated

b. heterogeneous

d. inhibited

____ 34. Adsorption of reactants on the surface of a metal catalyst changes the reaction rate by affecting the

a. concentration of the reactants.

c. properties of the reactants.

b. temperature of the system.

d. surface area of the reactants.

____ 35. A substance that slows down chemical processes is called a(n)

a. inhibitor.

c. catalyst.

b. reactant.

d. indicator.

____ 36. Catalysts generally affect chemical reactions by a. increasing the temperature of the system. b. increasing the surface area of the reactants. c. providing an alternate pathway with a lower activation energy. d. providing an alternate pathway with a higher activation energy.

____ 37. How is a heterogeneous catalyst different from the reactants in a chemical reaction? a. The mass of the catalyst is different. b. The chemical properties of the catalyst are different. c. The energy of the catalyst is different. d. The phase of the catalyst is different.

____ 38. In a net equation, catalysts a. are shown with the reactants. b. are shown with the products. c. are shown with both reactants and products. d. are not shown.

____ 39. For a cost-sensitive reaction, catalysts can be

a. thrown away.

c. regenerated and reused.

b. used as reaction inhibitors.

d. used as reaction indicators.

____ 40. A rate law relates a. reaction rate and temperature. b. reaction rate and concentrations of reactants. c. temperature and concentrations of reactants. d. energy and concentrations of reactants.

____ 41. The letter R in a rate law stands for a. a proportionality constant. b. concentration.

c. temperature. d. reaction rate.

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Name: ________________________

ID: A

____ 42. The value of k in a rate law a. is the same under all conditions. b. varies with concentration.

c. varies with time. d. varies with temperature.

____ 43. How are the units for a rate always expressed? change in concentration

a. unit time elapsed

b. ???change in concentration ^~ ? ???unit time elapsed ^~ unit time elapsed

c. change in concentration

d. unit time elapsed

____ 44. In the rate law for the following equation, R=k[A]n[B]m, the units for [A] and [B] are

a. g-1s-1.

c. M.

b. M-1s-1.

d. Ms-1.

____ 45. A reaction is zero order in reactant A and second order in reactant B. What happens to the reaction rate when the concentrations of both reactants are doubled? a. The reaction rate remains the same. b. The reaction rate increases by a factor of two. c. The reaction rate increases by a factor of four. d. The reaction rate increases by a factor of eight.

____ 46. If doubling the concentration of a reactant quadruples the rate of the reaction, the concentration of the

reactant appears in the rate law with a(n)

a. exponent of 1.

c. exponent of 4.

b. exponent of 2.

d. coefficient of 2.

____ 47. If a chemical reaction proceeds in a sequence of steps, the slowest step is called

a. the kinetic step.

c. the problem step.

b. the constant step.

d. the rate-determining step.

____ 48. At equilibrium, a. all reactions have ceased. b. only the forward reaction continues. c. only the reverse reaction continues. d. both the forward and reverse reactions continue.

____ 49. At equilibrium, a. the forward reaction rate is lower than the reverse reaction rate. b. the forward reaction rate is higher than the reverse reaction rate. c. the forward reaction rate is equal to the reverse reaction rate. d. no reactions take place.

____ 50. What two processes are at equilibrium in a saturated sugar solution?

a. evaporation and condensation

c. decomposition and synthesis

b. dissolving and crystallization

d. ionization and recombination

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