1. Flashcards for Unit 12

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

3. Conditions for Equilibrium
2-way process
Closed System
Conditions for Equilibrium

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

5. Physical: Phase & Solution Chemical
Types of Equilibria

6. A solution at equilibrium must be
Saturated
A solution at equilibrium must be

7. H2O(l)  H2O(g)
Phase Equilibrium

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

9. Solution Equilibrium Covalent Cmpd
C6H12O6(s)  C6H12O6(aq)
Solution Equilibrium Covalent Cmpd

10. Phase Equilibrium
H2O(g)  H2O(l)

11. NH4Cl(s)  NH4+(aq) + Cl-(aq)
Solution Equilibrium
NH4Cl(s)  NH4+(aq) + Cl-(aq)

12. Chemical Equilibrium – Haber Synthesis
N2(g) + 3H2(g)  2NH3(g) + heat
Chemical Equilibrium – Haber Synthesis

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

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

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

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

17. At what temperature can H2O(s) and H2O(l) exist in equilibrium?
0C or 273K
At what temperature can H2O(s) and H2O(l) exist in equilibrium?

18. At what temperature can H2O(g) and H2O(l) exist in equilibrium?
100C or 373K
At what temperature can H2O(g) and H2O(l) exist in equilibrium?

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

20. An increase in pressure favors which side?
CO2(g)  CO2(aq)
When P , more CO2 dissolves!
An increase in pressure favors which side?

21. N2(g) + 3H2(g)  2NH3(g) + heat
Equilibrium shifts to right.
Concentration of H2 . Concentration of NH3 . Temperature 
N2(g) + 3H2(g)  2NH3(g) + heat
What happens?
Stress

22. N2(g) + 3H2(g)  2NH3(g) + heat
Shifts to the side with fewer moles of gas, in this case the right.
4 moles
2 moles
N2(g) + 3H2(g)  2NH3(g) + heat
How does this system respond to an increase in pressure?

23. N2(g) + 3H2(g)  2NH3(g) + heat
Shifts to the side with more moles of gas, in this case the left.
N2(g) + 3H2(g)  2NH3(g) + heat
How does this system respond to a decrease in pressure?

24. H2(g) + I2(g) + heat  2HI(g)
This system has the same # of moles on each side. It cannot respond to pressure changes.
2 moles
2 moles
H2(g) + I2(g) + heat  2HI(g)
How does this system respond to a decrease in pressure?

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

26. N2(g) + 3H2(g)  2NH3(g) + heat
Equilibrium shifts to the left.
Concentration of N2 & H2 . Temperature .
N2(g) + 3H2(g)  2NH3(g) + heat
Stress
What happens?

27. N2(g) + 3H2(g)  2NH3(g) + heat
Equilibrium shifts to the right.
Concentration of N2 & H2 . Temperature .
N2(g) + 3H2(g)  2NH3(g) + heat
Stress
What happens?

28. N2(g) + 3H2(g)  2NH3(g) + heat
Equilibrium shifts to the left.
Concentration of N2 . Concentration of NH3 . Temperature .
N2(g) + 3H2(g)  2NH3(g) + heat
Stress
What happens?

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

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

31. Hproducts - Hreactants
Heat of reaction, H

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

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

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

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

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

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

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

39. Which phase change is endothermic?
Gas to liquid
Gas to solid
Solid to gas
Liquid to solid
Which phase change is endothermic?

40. Which phase change is exothermic?
Solid to gas
Liquid to gas
Solid to liquid
Liquid to solid
Which phase change is exothermic?

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

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

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

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

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

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

47. Entropy S

48. Enthalpy or Chemical Potential Energy

49. A perfect crystal at 0K
0 entropy?

50. Change in entropy Sproducts – Sreactants

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

52. Which phase has the greatest entropy?
Sgas >> Sliquid > Ssolid
Which phase has the greatest entropy?

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

54. Did the entropy increase or decrease?
CO2(g)  CO2(aq)
Decrease!
Did the entropy increase or decrease?

55. Did the entropy increase or decrease?
2H2O(l)  2H2(g) + O2(g)
Increase!
Did the entropy increase or decrease?

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

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

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
When will a change never occur?

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

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

61. Identify reactants, products, activated complex

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

69. Energetic Favorable Orientation
Effective Collisions

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

71. Absorbs Energy
Breaking Bonds …

72. Releases Energy
Making Bonds …

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
6 Factors that influence the rate of reaction

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

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

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

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

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

79. Does a catalyst change H?
NO.
Does a catalyst change H?

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

81. Which reacts faster in water: 1 cm3 of Na or 1 cm3 of Ca?
Nature of the metals
Which reacts faster in water: 1 cm3 of Na or 1 cm3 of Ca?

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

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