1. As the number of effective collisions between reacting particles increases, the rate of reaction (1) decreases (3) remains the same (2) increases

Transcription

1 1. As the number of effective collisions between reacting particles increases, the rate of reaction (1) decreases (3) remains the same (2) increases 2. The energy needed to start a chemical reaction is called (1) potential energy (3) activation energy (2) kinetic energy (4) ionization energy Base your answers to questions 6 and 7 on the table below, which represents the production of 50 milliliters of CO 2 in the reaction of HCl with NaHCO 3. Five trials were performed under different conditions as shown. (The same mass of NaHCO 3 was used in each trial.) 3. A piece of Mg(s) ribbon is held in a Bunsen burner flame and begins to burn according to the equation: 2Mg(s) + O 2 (g) 2MgO(s). The reaction begins because the reactants (1) are activated by heat from the Bunsen burner flame (2) are activated by heat from the burning magnesium (3) underwent an increase in entropy (4) underwent a decrease in entropy 4. Increasing the temperature increases the rate of a reaction by (1) lowering the activation energy (2) increasing the activation energy (3) lowering the frequency of effective collisions between reacting molecules (4) increasing the frequency of effective collisions between reacting molecules 5. Which conditions will increase the rate of a chemical reaction? (1) decreased temperature and decreased concentration of reactants (2) decreased temperature and increased concentration of reactants (3) increased temperature and decreased concentration of reactants (4) increased temperature and increased concentration of reactants 6. Which two trials could be used to measure the effect of surface area? (1) trials A and B (3) trials A and D (2) trials A and C (4) trials B and D 7. Which trial would produce the fastest reaction? (1) trial A (3) trial C (2) trial B (4) trial D 8. Given the reaction: Mg + 2 H 2 O Mg(OH) 2 + H 2 At which temperature will the reaction occur at the greatest rate? (1) 25ºC (3) 75ºC (2) 50ºC (4) 100ºC

2 9. Given the reaction: Zn(s) + 2 HCI(aq) - Zn 2+ (aq) + 2 Cl (aq) + H 2 (g) If the concentration of HCl(aq) is increased, the frequency of reacting collisions will (1) decrease, producing a decrease in the reaction rate (2) decrease, producing an increase in the reaction rate (3) increase, producing a decrease in the reaction rate (4) increase, producing an increase in the reaction rate 10. A 1.0-gram piece of zinc reacts with 5 milliliters of HCl(aq). Which of these conditions of concentration and temperature would produce the greatest rate of reaction? (1) 1.0 M HCl(aq) at 20. C (2) 1.0 M HCl(aq) at 40. C (3) 2.0 M HCl(aq) at 20. C (4) 2.0 M HCl(aq) at 40. C 11. In each of the four beakers shown below, a 2.0-centimeter strip of magnesium ribbon reacts with 100 milliliters of HCl(aq) under the conditions shown. In which beaker will the reaction occur at the fastest rate? (1) A (2) B (3) C (4) D

3 12. Which statement explains why the speed of some chemical reactions is increased when the surface area of the reactant is increased? (1) This change increases the density of the reactant particles. (2) This change increases the concentration of the reactant. (3) This change exposes more reactant particles to a possible collision. (4) This change alters the electrical conductivity of the reactant particles. 13. Beaker A contains a 1 gram piece of zinc and beaker B contains 1 gram of powdered zinc. If 100 milliliters of 0.1 M HCl is added to each of the beakers, how does the rate of reaction in beaker A compare to the rate of reaction in beaker B? (1) The rate in A is greater due to the smaller surface area of the zinc. (2) The rate in A is greater due to the larger surface area of the zinc. (3) The rate in B is greater due to the smaller surface area of the zinc. (4) The rate in B is greater due to the larger surface area of the zinc. 14. Which change would most likely increase the rate of a chemical reaction? (1) decreasing a reactant's concentration (2) decreasing a reactant's surface area (3) cooling the reaction mixture (4) adding a catalyst to the reaction mixture 15. Adding a catalyst to a chemical reaction changes the rate of reaction by causing (1) a decrease in the activation energy (2) an increase in the activation energy (3) a decrease in the heat of reaction (4) an increase in the heat of reaction 16. Which of the following best describes exothermic chemical reactions? (1) They never release heat. (2) They always release heat. (3) They never occur spontaneously. (4) They always occur spontaneously. 17. Given the reaction: Fe + S FeS + energy Which statement about this reaction is true? (1) It is endothermic. (2) It is exothermic. (3) The potential energy of the reactants is lower than the potential energy of the product. (4) The potential energy of the reactants is the same as the potential energy of the product. 18. Given the reaction: A + B C + D + heat Which statement best describes this reaction? (1) The forward reaction is exothermic, and the reverse reaction is always exothermic. (2) The forward reaction is exothermic, and the reverse reaction is always endothermic. (3) The forward reaction is exothermic, and the reverse reaction can be either exothermic or endothermic. (4) The forward reaction is endothermic, and the reverse reaction can be either endothermic or exothermic. 19. A student observed that when sodium hydroxide was dissolved in water, the temperature of the water increased. The student should conclude that the dissolving of sodium hydroxide (1) is endothermic (2) is exothermic (3) produces an acid solution (4) produces a salt solution 20. Given the balanced equation: Which statement best describes this process? (1) It is endothermic and entropy increases. (2) It is endothermic and entropy decreases. (3) It is exothermic and entropy increases. (4) It is exothermic and entropy decreases.

4 21. Which balanced equation represents an endothermic reaction? (1) C(s) + O 2 (g) CO 2 (g) (2) CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O( ) (3) N 2 (g) + 3H 2 (g) 2NH 3 (g) (4) N 2 (g) + O 2 (g) 2NO(g) 22. In a chemical reaction, the difference between the potential energy of the products and the potential energy of the reactants is the (1) heat of reaction (3) free energy (2) heat of fusion (4) activation energy 23. According to Reference Table I, what is the heat of reaction for the formation of two moles of H 2 O( ) from hydrogen and oxygen gas at 1 atmosphere and 298 K? (1) kj (3) 55.8 kj (2) kj (4) kj 24. Based on Reference Table I, which reaction is endothermic? (1) NaOH(s) Na + (aq) + OH (aq) (2) NH 4 Cl(s) NH 4 + (aq) + Cl (aq) (3) CO(g) + O 2 (g) CO 2 (g) (4) CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O( ) 25. Given the reaction: N 2 (g) + O 2 (g) kj 2 NO(g) What is the heat of formation of nitrogen (II) oxide in kj/mole? (1) ΔH = (3) ΔH = 91.3 (2) ΔH = 91.3 (4) ΔH = Based on Reference Table I, the formation of 1 mole of which of the following substances releases the greatest amount of energy? (1) C 2 H 2 (2) C 2 H 4 (3) CO 2 (4) H 2 O 27. According to Reference Table I, the dissolving of NH 4 Cl(s) in water is (1) exothermic and the heat of reaction is negative (2) exothermic and the heat of reaction is positive (3) endothermic and the heat of reaction is negative (4) endothermic and the heat of reaction is positive 28. According to Reference Table I, which compound is formed from its elements during an exothermic reaction? (1) HI(g) (2) CO 2 (g) (3) NO(g) (4) NO 2 (g) 29. Given the reaction: H 2 O( ) kj H 2 (g) + O 2 (g) Which statement describes the reverse reaction? (1) It is endothermic and releases 286 kj. (2) It is endothermic and absorbs 286 kj. (3) It is exothermic and releases 286 kj. (4) It is exothermic and absorbs 286 kj. 30. According to Reference Table U, which gas is formed from its elements by a spontaneous reaction? (1) NO(g) (2) NO 2 (g) (3) C 2 H 4 (g) (4) C 2 H 6 (g)

5 31. The graph below represents the potential energy changes that occur in a chemical reaction. Which letter represents the activated complex? Base your answers to questions 33 and 34 on the reaction coordinate shown below: (1) A (3) C (2) B (4) D 32. Base your answers on the potential energy diagram below. 33. Which interval represents the activation energy of the forward reaction? (1) A (3) C (2) B (4) D 34. Which interval represents the heat of reaction? (1) A (3) C (2) B (4) D 35. The graph below represents a chemical reaction. The potential energy of the activated complex is equal to the sum of (1) X + Y (3) X + Y + W (2) X + W (4) X + W + Z This reaction is best described as (1) endothermic, because energy is absorbed (2) endothermic, because energy is released (3) exothermic, because energy is absorbed (4) exothermic, because energy is released

6 36. Which interval on the potential energy diagram shown below represents the ΔH of the reaction 38. A potential energy diagram is shown below. a + b c + d? (1) 1 (3) 3 (2) 2 (4) The potential energy diagram below represents the reaction 2 KClO 3 2 KCl + 3 O 2. Which reaction would have the lowest activation energy? (1) the forward catalyzed reaction (2) the forward uncatalyzed reaction (3) the reverse catalyzed reaction (4) the reverse uncatalyzed reaction 39. Base your answer to the following question on the potential energy diagram of a chemical reaction shown below. Which numbered interval on the diagram would change when a catalyst is added? (1) 1 (3) 3 (2) 2 (4) 4 Which arrow represents the activation energy for the forward reaction? (1) A (3) C (2) B (4) D

7 40. The potential energy diagram of a chemical reaction is shown below. Which arrow represents the part of the reaction most likely to be affected by the addition of a catalyst? (1) A (3) C (2) B (4) D 41. A potential energy diagram of a chemical reaction is shown below. What is the difference between the potential energy of the reactants and the potential energy of the products? (1) 20. kcal (3) 60. kcal (2) 40. kcal (4) 80. kcal

8 42. Base your answers to the following questions on the information below. Cold packs are often used to prevent swelling of certain athletic injuries. The pack contains ammonium nitrate and water in separate compartments. When the pack is squeezed, the partition breaks mixing the components and forming a solution which turns very cold. Below is the reaction: NH 4 NO 3 (s) NH 4 NO 3 (l) a Based on the information above, is the reaction endothermic or exothermic? b Based on the information above, is there an increase or decrease in entropy of the system within the a cold pack if is used? Explain your answer. Base your answers to questions 43 and 44 on the information and diagram below, which represent the changes in potential energy that occur during the given reaction. Given the reaction: A + B C 43. a. Does the diagram illustrate an exothermic or an endothermic reaction? b. State one reason, in terms of energy, to support your answer. 44. On the diagram provided draw a dashed line to indicate a potential energy curve for the reaction if a catalyst is added.

9 45. Base your answers to the following questions on the information below. A hot pack contains chemicals that can be activated to produce heat. A cold pack contains chemicals that feel cold when activated. a Based on energy flow, state the type of chemical change that occurs in a hot pack. b A cold pack is placed on an injured leg. Indicate the direction of the flow of energy between the leg and the cold pack. c What is the Law of Conservation of Energy? Describe how the Law of Conservation of Energy applies to the chemical reaction that occurs in the hot pack. 46. Base your answer to the following question on the information below. 47. A student wishes to investigate how the reaction rate changes with a change in concentration of HCl(aq). Given the reaction: Zn(s) + HCl(aq) H 2 (g) + ZnCl 2 (aq) Identify one other variable that might affect the rate and should be held constant during this investigation. On the set of axes provided, sketch the potential energy diagram for an endothermic chemical reaction that shows the activation energy and the potential energy of the reactants and the potential energy of the products.

10 48. Base your answer to the following question on the information and potential energy diagram below. Chemical cold packs are often used to reduce swelling after an athletic injury. The diagram represents the potential energy changes when a cold pack is activated. Which lettered interval on the diagram represents the potential energy of the products? 49. Base your answer to the following question on the information below. Given the reaction at equilibrium: 2NO 2 (g) + 7H 2 (g) 2NH 3 (g) + 4H 2 O(g) kj Complete the potential energy diagram above for the forward reaction. Be sure your drawing shows the activation energy and the potential energy of the products.

11 50. Base your answer to the following question on the potential energy diagram below. What is the heat of reaction for the forward reaction?

12 Answer Key a exothermic b Examples: Energy flows from the injured leg to the cold pack. Heat flows from the higher temperature (the leg) to the lower temperature (the cold pack). The cold pack absorbs heat energy from the injured leg. c The energy released from the hot pack is equal to the energy absorbed by the surroundings. The total energy of the system (the hot pack) is equal to the total energy of the surroundings. Everything else is constant. 46. Examples: temperature; surface area of Zn; amount of Zn; Zn; concentration of Zn; [Zn] a) Endothermic b) Increase; because there is more disorder or randomness. 43. a. Endothermic b. Examples: -PE of product C is greater than PE of reactants A and B. -Product C absorbed energy and is at a higher PE than reactants A and B. 48. Allow credit for D Essay kj or 80 kj.