1. Flashcards for Unit 12

2. Equilibrium Rate of forward process = Rate of reverse process

3. Conditions for Equilibrium 2-way process Closed System

4. Dynamic Equilibrium Macroscopic level – looks constant. Microscopic level – lots of action

5. Types of Equilibria 1)Physical: Phase & Solution 2)Chemical

6. A solution at equilibrium must be Saturated

7. Phase Equilibrium H 2 O(l)  H 2 O(g)

8. Solution Equilibrium Ionic Cmpd NaCl(s)  Na + (aq) + Cl - (aq)

9. Solution Equilibrium Covalent Cmpd C 6 H 12 O 6 (s)  C 6 H 12 O 6 (aq)

10. H 2 O(g)  H 2 O(l) Phase Equilibrium

11. NH 4 Cl(s)  NH 4 + (aq) + Cl - (aq) Solution Equilibrium

12. Chemical Equilibrium – Haber Synthesis N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat

13. LeChatelier’s Principle A system at equilibrium will respond to remove a stress

14. What’s a stress for a chemical system? Change in temperature, pressure, or concentration

15. Catalyst Substance that increases the rate of a chemical reaction without itself being consumed.

16. Catalyst Does not shift the equilbrium point – the equilibrium concentrations are the same. You just get to equilibrium quicker.

17. At what temperature can H 2 O(s) and H 2 O(l) exist in equilibrium? 0  C or 273K

18. At what temperature can H 2 O(g) and H 2 O(l) exist in equilibrium? 100  C or 373K

19. Pressure Changes Only affect systems that have a gas in them

20. An increase in pressure favors which side? CO 2 (g)  CO 2 (aq) When P , more CO 2 dissolves!

21. N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat Equilibrium shifts to right. Concentration of H 2 . Concentration of NH 3 . Temperature  Stress What happens?

22. N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat Shifts to the side with fewer moles of gas, in this case the right. How does this system respond to an increase in pressure? 4 moles 2 moles

23. N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat Shifts to the side with more moles of gas, in this case the left. How does this system respond to a decrease in pressure?

24. H 2 (g) + I 2 (g) + heat  2HI(g) This system has the same # of moles on each side. It cannot respond to pressure changes. How does this system respond to a decrease in pressure? 2 moles

25. NaCl(s)  Na + (aq) + Cl - (aq) This system has no gases. It does NOT respond to pressure changes. How does this system respond to a change in pressure?

26. N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat Equilibrium shifts to the left. Concentration of N 2 & H 2 . Temperature . Stress What happens?

27. N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat Equilibrium shifts to the right. Concentration of N 2 & H 2 . Temperature . Stress What happens?

28. N 2 (g) + 3H 2 (g)  2NH 3 (g) + heat Equilibrium shifts to the left. Concentration of N 2 . Concentration of NH 3 . Temperature . Stress What happens?

29. Exothermic Reaction Energy is released: It flows from system to environment. Temperature of environment increases.

30. Endothermic Reaction Energy is absorbed: It flows from environment to system. Temperature of environment drops.

31. Heat of reaction,  H H products - H reactants

32. The difference between the potential energy of the products & the potential energy of the reactants? H products – H reactants or  H

33.  H for exothermic rxn  H is negative. System has net loss in energy.

34.  H is negative? Exothermic reaction. Products have less potential energy than reactants.

35.  H is positive? Endothermic reaction. Products have more potential energy than reactants.

36.  H for endothermic rxn  H is positive. System has net gain in energy.

37. A + B  C + D + heat Exothermic Reaction. Heat term is on product side.

38. A + B + heat  C + D Endothermic Reaction. Heat term is on reactant side.

39. Which phase change is endothermic? a)Gas to liquid b)Gas to solid c)Solid to gas d)Liquid to solid

40. Which phase change is exothermic? a)Solid to gas b)Liquid to gas c)Solid to liquid d)Liquid to solid

41. A reaction occurs in water & the temperature of the water increases. Endo or Exo? Exothermic

42. A reaction occurs in water & the temperature of the water decreases. Endo or Exo? Endothermic

43. A + B  C + D.  H = -45 kJ. What is  H for C + D  A + B?  H = +45 kJ

44. A + B  C + D.  H = -45 kJ. What is  H for: 2A + 2B  2C + 2D?  H = -90 kJ

45. Entropy Degree of disorder or chaos in a system.

46. Entropy The more degrees of freedom a system has, the higher the entropy.

47. S Entropy

48. H Enthalpy or Chemical Potential Energy

49. 0 entropy? A perfect crystal at 0K

50. SS Change in entropy S products – S reactants

51. Which phase has the greatest entropy? Gas phase – the molecules have more ways of moving & more places to be!

52. Which phase has the greatest entropy? S gas >> S liquid > S solid

53. Did the entropy increase or decrease? NaCl(s)  Na + (aq) + Cl - (aq) Increase!

54. Did the entropy increase or decrease? CO 2 (g)  CO 2 (aq) Decrease!

55. Did the entropy increase or decrease? 2H 2 O(l)  2H 2 (g) + O 2 (g) Increase!

56. Spontaneous Process Physical or Chemical change that occurs with no outside intervention. (Supplying activation energy does not count!)

57. Nature is lazy & disorganized. Nature favors: Negative value for  H: Net loss Positive value for  S: Net gain

58. When will a change never occur? When both factors go against nature: Positive value for  H: Net gain in energy. Negative value for  S: Net loss in chaos

59. Endo: starts low, ends high Endo or Exo?

60. Exo: starts high, ends low Endo or Exo?

61. Reactants Identify reactants, products, activated complex Activated Complex Products

62. Potential energy of reactants Identify the arrow

63. Activation energy of forward rxn Identify the arrow

64. Heat of reaction Identify the arrow

65. Activation energy of reverse reaction Identify the arrow

66. Potential energy of activated complex Identify the arrow

67. Potential energy of products Identify the arrow

68. Collision Theory Effective collisions between reacting particles must occur for a reaction to take place.

69. Effective Collisions Energetic Favorable Orientation

70. Rate of reaction The speed of the reaction. The faster it occurs, the greater the rate.

71. Breaking Bonds … Absorbs Energy

72. Making Bonds … Releases Energy

73. 6 Factors that influence the rate of reaction Nature of reactants (ionic or covalent) Temperature Concentration Pressure (for gases) Surface area (for heterogeneous reactions) Presence of a catalyst

74. Raising the temperature increases the reaction rate by Increasing both the number of collisions and the efficiency of the collisions.

75. As the concentrations of the reactants , the rate of rxn … increases

76. As the pressure on gas-phase reactants , the rate of rxn … Increases.

77. Which 4.0-gram Zn sample will react faster with acid, and why? a)Lump b)Bar c)Powdered d)Sheet metal More surface area

78. How does a catalyst work? Provides an alternate reaction pathway with a lower activation energy.

79. Does a catalyst change  H? NO.

80. Which reacts faster: ions in solution or covalent molecules? Ions in solution.

81. Which reacts faster in water: 1 cm 3 of Na or 1 cm 3 of Ca? 1 cm 3 of Na - Nature of the metals

82. Which is usually slower, an organic reaction or an inorganic reaction? Organic, because organic particles contain covalent bonds.

83. Lowers the activation energy. Effect of a catalyst?

84. Potential energy of reactants Identify the arrow

85. Activation energy of forward rxn Identify the arrow

86. Activation energy of reverse rxn Identify the arrow

87. Potential energy of activated complex Identify the arrow

88. Heat of reaction Identify the arrow

89. Potential energy of products Identify the arrow