8. A piece of Mg(s) ribbon is held in a Bunsen burner flame and begins to burn according to the equation: 2Mg(s) + O2 (g) 2MgO(s).

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1 1. Which event must always occur for a chemical reaction to take place? A) formation of a precipitate B) formation of a gas C) effective collisions between reacting particles D) addition of a catalyst to the reaction system 2. Why can an increase in temperature lead to more effective collisions between reactant particles and an increase in the rate of a chemical reaction? A) The activation energy of the reaction increases. B) The activation energy of the reaction decreases. C) The number of molecules with sufficient energy to react increases. D) The number of molecules with sufficient energy to react decreases. 3. As the temperature of a chemical reaction in the gas phase is increased, the rate of the reaction increases because A) fewer particle collisions occur B) more effective particle collisions occur C) the required activation energy increases D) the concentration of the reactants increases 4. What is required for a chemical reaction to occur? A) standard temperature and pressure B) a catalyst added to the reaction system C) effective collisions between reactant particles D) an equal number of moles of reactants and products 5. A reaction is most likely to occur when reactant particles collide with A) proper energy, only B) proper orientation, only C) both proper energy and proper orientation D) neither proper energy nor proper orientation 6. The energy needed to start a chemical reaction is called A) potential energy B) kinetic energy C) activation energy D) ionization energy 7. A chemical reaction between iron atoms and oxygen molecules can only occur if A) the particles are heated B) the atmospheric pressure decreases C) there is a catalyst present D) there are effective collisions between the particle 8. A piece of Mg(s) ribbon is held in a Bunsen burner flame and begins to burn according to the equation: 2Mg(s) + O2 (g) 2MgO(s). The reaction begins because the reactants A) are activated by heat from the Bunsen burner flame B) are activated by heat from the burning magnesium C) underwent an increase in entropy D) underwent a decrease in entropy 9. For a reaction at equilibrium, which change can increase the rates of the forward and reverse reactions? A) a decrease in the concentration of the reactants B) a decrease in the surface area of the products C) an increase in the temperature of the system D) an increase in the activation energy of the forward reaction 10. At kpa and 298 K, a 1.0-mole sample of which compound absorbs the greatest amount of heat as the entire sample dissolves in water? A) LiBr B) NaCl C) NaOH D) NH4Cl 11. Given the reaction: Mg + 2 H2O Mg(OH)2 + H2 At which temperature will the reaction occur at the greatest rate? A) 25ºC B) 50ºC C) 75ºC D) 100ºC 12. A 5.0-gram sample of zinc and a 50.-milliliter sample of hydrochloric acid are used in a chemical reaction. Which combination of these samples has the fastest reaction rate? A) a zinc strip and 1.0 M HCl(aq) B) a zinc strip and 3.0 M HCl(aq) C) zinc powder and 1.0 M HCl(aq) D) zinc powder and 3.0 M HCl(aq)

2 13. 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? A) 1.0 M HCl(aq) at 20. C B) 1.0 M HCl(aq) at 40. C C) 2.0 M HCl(aq) at 20. C D) 2.0 M HCl(aq) at 40. C 14. As the concentration of reacting particles increases, the rate of reaction generally A) decreases B) increases C) remains the same 15. Given the reaction at 25 C: Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g) The rate of this reaction can be increased by using 5.0 grams of powdered zinc instead of a 5.0-gram strip of zinc because the powdered zinc has A) lower kinetic energy B) lower concentration C) more surface area D) more zinc atoms 16. An increase in the surface area of reactants in a heterogeneous reaction will result in A) a decrease in the rate of the reaction B) an increase in the rate of the reaction C) a decrease in the heat of reaction D) an increase in the heat of reaction 17. Given the balanced equation representing a reaction: 18. Compared to the rate of inorganic reactions, the rate of organic reactions generally is A) slower because organic particles are ions B) slower because organic particles contain covalent bonds C) faster because organic particles are ions D) faster because organic particles contain covalent bonds 19. Which statement best explains the role of a catalyst in a chemical reaction? A) A catalyst is added as an additional reactant and is consumed but not regenerated. B) A catalyst limits the amount of reactants used. C) A catalyst changes the kinds of products produced. D) A catalyst provides an alternate reaction pathway that requires less activation energy. 20. Compared with the rate of an inorganic reaction, the rate of an organic reaction is usually A) faster, because the organic particles are ions B) faster, because the organic particles are molecules C) slower, because the organic particles are ions D) slower, because the organic particles are molecules 21. In what type of reaction do the products of the reaction always possess more potential energy than the reactants? A) endothermic B) exothermic C) spontaneous D) redox Fe(s) + 2HCl(aq) FeCl2 (aq) + H2(g) This reaction occurs more quickly when powdered iron is used instead of a single piece of iron of the same mass because the powdered iron A) acts as a better catalyst than the single piece of iron B) absorbs less energy than the single piece of iron C) has a greater surface area than the single piece of iron D) is more metallic than the single piece of iron

3 22. Given the balanced equation: Which statement best describes this process? A) It is endothermic and entropy increases. B) It is endothermic and entropy decreases. C) It is exothermic and entropy increases. D) It is exothermic and entropy decreases. 23. A thermometer is in a beaker of water. Which statement best explains why the thermometer reading initially increases when LiBr(s) is dissolved in the water? A) The entropy of the LiBr(aq) is greater than the entropy of the water. B) The entropy of the LiBr(aq) is less than the entropy of the water. C) The dissolving of the LiBr(s) in water is an endothermic process. D) The dissolving of the LiBr(s) in water is an exothermic process. 24. A student observed that the temperature of water increased when a salt was dissolved in it. The student should conclude that dissolving the salt was A) involved in the formation of an acidic solution B) involved in the formation of a basic solution C) an exothermic reaction D) an endothermic reaction 25. Salt A and salt B were dissolved separately in 100-milliliter beakers of water. The water temperatures were measured and recorded as shown in the table below. Salt A Salt B Initial water temperature: 25.1ºC 25.1ºC Final water temperature: 30.2ºC 20.0ºC Which statement is a correct interpretation of these data? A) The dissolving of only salt A was endothermic. B) The dissolving of only salt B was exothermic. C) The dissolving of both salt A and salt B was endothermic. D) The dissolving of salt A was exothermic and the dissolving of salt B was endothermic. 26. According to Reference Table I, heat is liberated during the formation of the compound A) nitrogen (II) oxide (g) B) ethyne (g) C) water (g) D) hydrogen iodide (g) 27. Assume that the potential energy of the products in a chemical reaction is 60 kilojoules. This reaction would be exothermic if the potential energy of the reactants were A) 50 kj B) 20 kj C) 30 kj D) 80 kj 28. Which term refers to the difference between the potential energy of the products and the potential energy of the reactants for any chemical change? A) heat of deposition B) heat of fusion C) heat of reaction D) heat of vaporization 29. Based on Reference Table I, which reaction is endothermic? A) NaOH(s) Na + (aq) + OH (aq) B) NH4Cl(s) NH4 + (aq) + Cl (aq) C) CO(g) + O2(g) CO2(g) D) CH4(g) + 2 O2(g) CO2(g) + 2 H2O( ) 30. According to Reference Table I, what is the heat of reaction for the formation of two moles of H2O( ) from hydrogen and oxygen gas at 1 atmosphere and 298 K? A) kj B) kj C) 55.8 kj D) kj 31. According to Reference Table U, which gas is formed from its elements by a spontaneous reaction? A) NO(g) B) NO2(g) C) C2H4(g) D) C2H6(g)

4 32. In the potential energy diagram below, which letter represents the potential energy of the activated complex? 34. Given the potential energy diagram for a chemical reaction: A) A B) B C) C D) D 33. When a spark is applied to a mixture of hydrogen and oxygen, the gases react explosively. Which potential energy diagram best represents the reaction? A) B) C) D) Which statement correctly describes the energy changes that occur in the forward reaction? A) The activation energy is 10. kj and the reaction is endothermic. B) The activation energy is 10. kj and the reaction is exothermic. C) The activation energy is 50. kj and the reaction is endothermic. D) The activation energy is 50. kj and the reaction is exothermic.

5 35. Given the reaction: S(s) + O2(g) SO2(g) + energy Which diagram best represents the potential energy changes for this reaction? A) 36. The potential energy diagram below represents a reaction. B) C) Which arrow represents the activation energy of the forward reaction? A) A B) B C) C D) D 37. Base your answer to the following question on the potential energy diagram below, which represents the reaction: A + B C + energy. D) Which numbered interval will change with the addition of a catalyst to the system? A) 1 B) 2 C) 3 D) 4

6 38. The potential energy diagram of a chemical reaction is shown below. 42. Given the equation representing a system at equilibrium: 2SO2(g) + O2(g) 2SO3(g) Which letter in the diagram represents the heat of reaction ( H)? A) A B) B C) C D) D 39. 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? A) 20. kcal B) 40. kcal C) 60. kcal D) 80. kcal 40. A chemical reaction is at equilibrium. Compared to the rate of the forward reaction, the rate of the reverse reaction is A) faster and more reactant is produced B) faster and more product is produced C) the same and the reaction has stopped D) the same and the reaction continues in both directions 41. Given the reaction system in a closed container at equilibrium and at a temperature of 298 K: N2O4(g) 2NO2(g) The measurable quantities of the gases at equilibrium must be A) decreasing B) increasing C) equal D) constant At equilibrium, the concentration of A) SO2(g) must equal the concentration of SO3(g) B) SO2(g) must be constant C) O2(g) must equal the concentration of SO2(g) D) O2(g) must be decreasing 43. When AgNO3(aq) is mixed with NaCl(aq), a reaction occurs which tends to go to completion and not reach equilibrium because A) a gas is formed B) water is formed C) a weak acid is formed D) a precipitate is formed 44. Some solid KNO3 remains at the bottom of a stoppered flask containing a saturated KNO3(aq) solution at 22 C. Which statement explains why the contents of the flask are at equilibrium? A) The rate of dissolving is equal to the rate of crystallization. B) The rate of dissolving is greater than the rate of crystallization. C) The concentration of the solid is equal to the concentration of the solution. D) The concentration of the solid is greater than the concentration of the solution. 45. Given the equation representing a system at equilibrium: When the concentration of Cl (aq) is increased, the concentration of Ag + (aq) A) decreases, and the amount of AgCl(s) increases B) decreases, and the amount of AgCl(s) decreases C) increases, and the amount of AgCl(s) increases D) increases, and the amount of AgCl(s) decreases

7 46. Given the reaction: AgI(s) «Ag + (aq) + I (aq) Solution equilibrium is reached in the system when A) dissolving stops occurring B) crystallization stops occurring C) both dissolving and crystallization stops occurring D) dissolving occurs at the same rate that crystallization occurs 47. Given the equilibrium at kpa: H2O(s) «H2O( ) At what temperature does this equilibrium occur? A) 100 K B) 273 K C) 298 K D) 373 K 48. Which description applies to a system in a sealed flask that is half full of water? A) Only evaporation occurs, but it eventually stops. B) Only condensation occurs, but it eventually stops. C) Neither evaporation nor condensation occurs. D) Both evaporation and condensation occur. 49. Given the reaction at equilibrium: A(g) «B(g) + C( ) Which equilibrium constant indicates an equilibrium mixture with the smallest concentration of B(g)? A) Keq = B) Keq = C) Keq = D) Keq = Given the equation: H2(g) + I2(g) «2 HI(g) Which statement is always true when this reaction has reached chemical equilibrium? A) [H2] [I2] > [HI] B) [H2] [I2] < [HI] C) [H2], [I2], and [HI] are all equal. D) [H2], [I2], and [HI] remain constant. 51. Given the reaction at equilibrium: A2(g) + 3 B2(g) «2 AB3(g) + heat Which change will affect the equilibrium constant for this reaction? A) increasing the concentration of A 2(g) B) decreasing the concentration of B 2(g) C) increasing the temperature D) decreasing the pressure 52. Given the reaction at equilibrium: 2 SO2(g) + O2(g) «2 SO3(g) + heat The concentration of SO3(g) may be increased by A) decreasing the concentration of SO2(g) B) decreasing the concentration of O2(g) C) increasing the pressure D) increasing the temperature 53. Given the reaction at equilibrium: H2(g) + Cl2(g) «2 HCl(g) As the pressure increases at constant temperature, the number of moles of HCl A) decreases B) increases C) remains the same 54. Ammonia is produced commercially by the Haber reaction: N2(g) + 3 H2(g) «2 NH3(g) + heat The formation of ammonia is favored by A) an increase in pressure B) a decrease in pressure C) removal of N2(g) D) removal of H2(g) 55. Given the reaction at equilibrium: 4 HCl(g) + O2(g) «2 Cl2(g) + 2 H2O(g) If the pressure on the system is increased, the concentration of Cl2(g) will A) decrease B) increase C) remain the same

8 56. Given the system at equilibrium: H2(g) + F2(g) 2 HF(g) + heat Which change will not shift the point of equilibrium? A) changing the pressure B) changing the temperature C) changing the concentration of H2(g) D) changing the concentration of HF(g) 57. Given the reaction at equilibrium: A(g) + B(g) C(g) + D(g) The addition of a catalyst will A) shift the equilibrium to the right B) shift the equilibrium to the left C) increase the rate of forward and reverse reactions equally D) have no effect on the forward or reverse reactions 58. What will happen if a catalyst is added to the system at equilibrium? A + B «AB A) The equilibrium concentration of AB will increase. B) The equilibrium concentration of AB will decrease. C) The rates of the forward and reverse reactions will change. D) The equilibrium constant for the reaction will change. 59. Given the equation representing a reaction at equilibrium: N2(g) + 3H2(g) 2NH3(g) 60. Given the reaction at equilibrium: N2(g) + O2(g) + energy 2 NO(g) Which change will result in a decrease in the amount of NO(g) formed? A) decreasing the pressure B) decreasing the concentration of N2(g) C) increasing the concentration of O2(g) D) increasing the temperature 61. Given the reaction at equilibrium: A2(g) + B2(g) «2 AB(g) + heat Which stress on the system at equilibrium will increase the concentration of AB(g)? A) decreasing the concentration of A 2(g) B) increasing the concentration of B 2(g) C) decreasing the pressure D) increasing the temperature 62. Given the reaction at equilibrium: N2(g) + 3 H2(g) 2 NH3(g) + heat At constant temperature, which changes would produce a greater yield of NH3(g)? A) decreasing the pressure and decreasing the concentration of N2(g) B) decreasing the pressure and increasing the concentration of N2(g) C) increasing the pressure and decreasing the concentration of N2(g) D) increasing the pressure and increasing the concentration of N2(g) What occurs when the concentration of H2(g) is increased? A) The equilibrium shifts to the left, and the concentration of N2(g) decreases. B) The equilibrium shifts to the left, and the concentration of N2(g) increases. C) The equilibrium shifts to the right, and the concentration of N2(g) decreases. D) The equilibrium shifts to the right, and the concentration of N2(g) increases

9 63. Given the balanced equation representing a reaction: 2HCl(aq) + Na2S2O3(aq) S(s) + H2SO3(aq) + 2NaCl(aq) Decreasing the concentration of Na2S2O3(aq) decreases the rate of reaction because the A) activation energy decreases B) activation energy increases C) frequency of effective collisions decreases D) frequency of effective collisions increases 64. Given the reaction at equilibrium: 2 SO2(g) + O2(g) «2 SO3(g) + 44 kcal Which change will increase the concentration of SO3(g)? A) increasing the temperature B) increasing the concentration of O2(g) C) decreasing the pressure D) decreasing the concentration of SO2(g) 65. Given the reaction at equilibrium: 2 CO(g) + O2(g) «2 CO2(g) When the reaction is subjected to stress, a change will occur in the concentration of A) reactants, only B) products, only C) both reactants and products D) neither reactants nor products 66. A saturated solution is represented by the equation AgCl(s) + heat «Ag + (aq) + Cl (aq). Which change will cause an increase in the amount of AgCl(s)? A) a decrease in pressure B) an increase in temperature C) a decrease in the concentration of Ag + (aq) D) an increase in the concentration of Cl (aq) 67. Given the reaction at equilibrium: N2(g) + 3H2(g) 2NH3(g) kJ What occurs when the concentration of H2(g) is increased? A) The rate of the forward reaction increases and the concentration of N2(g) decreases. B) The rate of the forward reaction decreases and the concentration of N2(g) increases. C) The rate of the forward reaction and the concentration of N2(g) both increase. D) The rate of the forward reaction and the concentration of N2(g) both decrease. 68. Given the system at equilibrium: N2O4(g) kj 2 NO2(g) What will be the result of an increase in temperature at constant pressure? A) The equilibrium will shift to the left, and the concentration of NO2(g) will decrease. B) The equilibrium will shift to the left, and the concentration of NO2(g) will increase. C) The equilibrium will shift to the right, and the concentration of NO2(g) will decrease. D) The equilibrium will shift to the right, and the concentration of NO2(g) will increase. 69. Given the reaction for the Haber process: N2 + 3 H2 «2 NH3 + heat The temperature of the reaction is raised in order to A) increase the percent yield of nitrogen B) increase the rate of formation of ammonia C) affect the forward reaction rate most D) affect the reverse reaction rate least

10 70. An increase in the temperature of a system at equilibrium favors the A) endothermic reaction and decreases its rate B) endothermic reaction and increases its rate C) exothermic reaction and decreases its rate D) exothermic reaction and increases its rate 71. Given the reaction at equilibrium: The equilibrium will shift to the right if the A) temperature increases B) temperature decreases C) pressure increases D) pressure decreases 72. Given the equilibrium reaction in a closed system: H2(g) + I2(g) + heat 2 HI(g) What will be the result of an increase in temperature? A) The equilibrium will shift to the left and [H2] will increase. B) The equilibrium will shift to the left and [H2] will decrease. C) The equilibrium will shift to the right and [HI] will increase. D) The equilibrium will shift to the right and [HI] will decrease. 73. Given the equilibrium system: 2 A(g) + B(g) + 10 kcal «C(g) Which conditions would yield the most product? A) low temperature and high pressure B) low temperature and low pressure C) high temperature and high pressure D) high temperature and low pressure 74. Given the equation representing a reaction at equilibrium: H2(g) + I2(g) + heat 2HI(g) Which change favors the reverse reaction? A) decreasing the concentration of HI(g) B) decreasing the temperature C) increasing the concentration of I2(g) D) increasing the pressure 75. Given the system at equilibrium: AgCl(s) «Ag + (aq) + Cl (aq) When NaCl(s) is added to the system, the equilibrium will shift to the A) right and the concentration of AgCl(s) will decrease B) right and the concentration of AgCl(s) will increase C) left and the concentration of Ag + (aq) will decrease D) left and the concentration of Ag + (aq) will increase 76. Given the solution at equilibrium: CaSO4(s) Ca 2+ (aq) + SO4 2- (aq) When Na2SO4 is added to the system, how will the equilibrium shift? A) The amount of CaSO4(s) will decrease, and the concentration of Ca 2+ (aq) will decrease. B) The amount of CaSO4(s) will decrease, and the concentration of Ca 2+ (aq) will increase. C) The amount of CaSO4(s) will increase, and the concentration of Ca 2+ (aq) will decrease. D) The amount of CaSO4(s) Will increase, and the concentration of Ca 2+ (aq) will increase. 77. Given the equation: As NaCl(s) dissolves in the solution, temperature remaining constant, the Ag + (aq) concentration will A) decrease as the amount of AgCl(s) decreases B) decrease as the amount of AgCl(s) increases C) increase as the amount of AgCl(s) decreases D) increase as the amount of AgCl(s) increases

11 78. Given the system at equilibrium: AgCl(s) «Ag + (aq) + Cl (aq) When 0.1 M HCl is added to the system, the point of equilibrium will shift to the A) right and the concentration of Ag + will decrease B) right and the concentration of Ag + will increase C) left and the concentration of Ag + (aq) will decrease D) left and the concentration of Ag + (aq) will increase 79. Which reaction results in an increase in entropy? A) CO2(g) CO2(s) B) H2O( ) H2O(s) C) Ca(s) + 2 H2O( ) Ca(OH)2(aq) + H2(g) D) NaCl(aq) + AgNO3(aq) AgCl(s) + NaNO3(aq) 80. The entropy of a sample of H2O increases as the sample changes from a A) gas to a liquid B) gas to a solid C) liquid to a gas D) liquid to a solid 81. Systems in nature tend to undergo changes toward A) lower energy and lower entropy B) lower energy and higher entropy C) higher energy and lower entropy D) higher energy and higher entropy 82. As the reactants are converted to product in the reaction A(g) + B(g) C(s), the entropy of the system A) decreases B) increases C) remains the same 83. Which phrase best describes the reaction below? 84. Systems in nature tend to undergo changes toward A) lower energy and less disorder B) lower energy and more disorder C) higher energy and less disorder D) higher energy and more disorder 85. Which 1-mole sample has the least entropy? A) Br2(s) at 266 K B) Br2( ) at 266 K C) Br2( ) at 332 K D) Br2(g) at 332 K 86. A reaction will be spontaneous if it results in products that have A) lower potential energy and less randomness B) lower potential energy and more randomness C) greater potential energy and less randomness D) greater potential energy and more randomness 87. When a reaction is exothermic and the products have more entropy than the reactants, the reaction is A) spontaneous, with a negative DG B) spontaneous, with a positive DG C) non-spontaneous, with a negative DG D) non-spontaneous, with a positive DG 88. Which condition is necessary for a chemical reaction to occur spontaneously? A) S must be negative. B) S must be positive. C) G must be negative. D) G must be positive. 89. Which potential energy diagram indicates a reaction can occur spontaneously? A) B) A) exothermic with an increase in entropy B) exothermic with a decrease in entropy C) endothermic with an increase in entropy D) endothermic with a decrease in entropy C) D)

12 90. According to Reference Table U, which compound is spontaneously formed even though the reaction is endothermic? A) ICl(g) B) CO2(g) C) H2O( ) D) Al2O3(s) 91. Which compound forms spontaneously from its elements at 1 atm and 298 K? A) C2H2(g) B) C2H4(g) C) HF(g) D) HI(g) 92. The change in the free energy of a reaction ( G) is equal to A) B) C) D) 93. Based on Reference Table U, the compound which could form spontaneously under standard conditions from its elements is A) HF B) HI C) NO D) NO2 94. Which equation correctly represents the free energy change in a chemical reaction? A) B) C) D)

13 Answer Key Kinetics & Equilibrium 1. C 2. C 3. B 4. C 5. C 6. C 7. D 8. A 9. C 10. D 11. D 12. D 13. D 14. B 15. C 16. B 17. C 18. B 19. D 20. D 21. A 22. A 23. D 24. C 25. D 26. C 27. D 28. C 29. B 30. B 31. D 32. B 33. B 34. B 35. A 36. B 37. B 38. B 39. A 40. D 41. D 42. B 43. D 44. A 45. A 46. D 47. B 48. D 49. A 50. D 51. C 52. C 53. C 54. A 55. B 56. A 57. C 58. C 59. C 60. B 61. B 62. D 63. C 64. B 65. C 66. D 67. A 68. D 69. B 70. B 71. A 72. C 73. C 74. B 75. C 76. C 77. B 78. C 79. C 80. C 81. B 82. A 83. A 84. B 85. A 86. B 87. A 88. C 89. D 90. A 91. C 92. C 93. A 94. B