1. Using Everyday Equations
12.1
Using Everyday Equations
A balanced chemical equation provides the same kind of quantitative information that a recipe does.
A cookie recipe tells you the number of cookies that you can expect to make from the listed amounts of ingredients. Using Models How can you express a cookie recipe as a balanced equation?

2. Using Balanced Chemical Equations
12.1
Using Balanced Chemical Equations
Using Balanced Chemical Equations
How do chemists use balanced chemical equations?

3. Using Balanced Chemical Equations
12.1
Using Balanced Chemical Equations
Chemists use balanced chemical equations as a basis to calculate how much reactant is needed or product is formed in a reaction.
The calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry.

4. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
A balanced chemical equation can be interpreted in terms of different quantities, including numbers of atoms, molecules, or moles; mass; and volume.

5. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
Number of Atoms
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

6. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
Number of Molecules
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

7. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
Moles
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

8. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
Mass
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

9. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
Volume
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

10. Interpreting Chemical Equations
12.1
Interpreting Chemical Equations
The balanced chemical equation for the formation of ammonia can be interpreted in several ways. Predicting How many molecules of NH3 could be made from 5 molecules of N2 and 15 molecules of H2?

11. Mass Conservation in Chemical Reactions
12.1
Mass Conservation in Chemical Reactions
Mass and atoms are conserved in every chemical reaction.

12. Writing and Using Mole Ratios
12.2
Writing and Using Mole Ratios
In chemical calculations, mole ratios are used to convert between moles of reactant and moles of product, between moles of reactants, or between moles of products.

13. 12.2
Manufacturing plants produce ammonia by combining nitrogen with hydrogen. Ammonia is used in cleaning products, fertilizers, and in the manufacture of other chemicals.

14. 12.2

15. 12.2

16. for Sample Problem 12.2

17. 12.3
In this Hubble Space Telescope image, clouds of condensed ammonia are visible covering the surface of Saturn.

18. 12.3

19. 12.3

20. for Sample Problem 12.3 `

21. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
Other Stoichiometric Calculations
What is the general procedure for solving a stoichiometric problem?

22. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
In a typical stoichiometric problem, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole, as the problem requires.

23. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
Solution Diagram
This general solution diagram indicates the steps necessary to solve a mass-mass stoichiometry problem: convert mass to moles, use the mole ratio, and then convert moles to mass. Inferring Is the given always a reactant?

24. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
Problem-Solving Approach
With your knowledge of conversion factors and this problem-solving approach, you can solve a variety of stoichiometric problems. Identifying What conversion factor is used to convert moles to representative particles?

25. 12.4
The electrolysis of water causes it to decompose into hydrogen and oxygen.

26. 12.4

27. 12.4

28. for Sample Problem 12.4

29. 12.5

30. 12.5

31. 12.5

32. for Sample Problem 12.5

33. 12.6

34. 12.6

35. 12.6

36. 12.6

37. for Sample Problem 12.5

38. Writing and Using Mole Ratios
12.2
Writing and Using Mole Ratios
In chemical calculations, mole ratios are used to convert between moles of reactant and moles of product, between moles of reactants, or between moles of products.

39. 12.2
Manufacturing plants produce ammonia by combining nitrogen with hydrogen. Ammonia is used in cleaning products, fertilizers, and in the manufacture of other chemicals.

40. 12.2

41. 12.2

42. for Sample Problem 12.2

43. Writing and Using Mole Ratios
12.2
Writing and Using Mole Ratios
Mass-Mass Calculations

44. 12.3
In this Hubble Space Telescope image, clouds of condensed ammonia are visible covering the surface of Saturn.

45. 12.3

46. 12.3

47. for Sample Problem 12.3 `

48. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
Other Stoichiometric Calculations
What is the general procedure for solving a stoichiometric problem?

49. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
In a typical stoichiometric problem, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole, as the problem requires.

50. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
Solution Diagram
This general solution diagram indicates the steps necessary to solve a mass-mass stoichiometry problem: convert mass to moles, use the mole ratio, and then convert moles to mass. Inferring Is the given always a reactant?

51. Other Stoichiometric Calculations
12.2
Other Stoichiometric Calculations
Problem-Solving Approach
With your knowledge of conversion factors and this problem-solving approach, you can solve a variety of stoichiometric problems. Identifying What conversion factor is used to convert moles to representative particles?

52. 12.4
The electrolysis of water causes it to decompose into hydrogen and oxygen.

53. 12.4

54. 12.4

55. for Sample Problem 12.4

56. 12.5

57. 12.5

58. 12.5

59. for Sample Problem 12.5

60. 12.6

61. 12.6

62. 12.6

63. 12.6

64. for Sample Problem 12.5

65. Limiting Reagent and Percent Yield
12.3
Limiting Reagent and Percent Yield
If a carpenter had two tabletops and seven table legs, he could only build one four-legged table. The number of table legs is the limiting factor in the construction of four-legged tables. Similarly, in chemistry, the amount of product made in a chemical reaction may be limited by the amount of one or more of the reactants. 65

66. Limiting and Excess Reagents
12.3
Limiting and Excess Reagents
In a chemical reaction, an insufficient quantity of any of the reactants will limit the amount of product that forms.
The limiting reagent is the reagent that determines the amount of product that can be formed by a reaction. 66

67. Limiting and Excess Reagents
12.3
Limiting and Excess Reagents
In the reaction of nitrogen and hydrogen, hydrogen is the limiting reagent. Nitrogen is the reagent that is not completely used up in the reaction. The reagent that is not used up is called the excess reagent. 67

68. Limiting and Excess Reagents
12.3
Limiting and Excess Reagents
The Chemical Equation for the Preparation of Ammonia
The “recipe” calls for 3 molecules of H2 for every 1 molecule of N2 . In this particular experiment, H2 is the limiting reagent and N2 is in excess. Inferring How would the amount of products formed change if you started with four molecules of N2 and three molecules of H2? 68

69. 12.7 69

70. 12.7 70

71. 12.8 71

72. 12.8 72

73. 12.8 73

74. 12.8 74

75. for Sample Problem 12.7 75

76. for Sample Problem 12.8 76

77. Percent Yield 12.3 What does the percent yield of a reaction measure?77

78. 12.3
Percent Yield
The percent yield is a measure of the efficiency of a reaction carried out in the laboratory.
A batting average is actually a percent yield. 78

79. 12.3
Percent Yield
The theoretical yield is the maximum amount of product that could be formed from given amounts of reactants.
In contrast, the amount of product that actually forms when the reaction is carried out in the laboratory is called the actual yield. 79

80. 12.3
Percent Yield
The percent yield is the ratio of the actual yield to the theoretical yield expressed as a percent. 80

81. 12.9 81

82. 12.9 82

83. 12.9 83

84. for Sample Problem 12.9 84

85. 12.10 85

86. 12.10 86

87. 12.10 87

88. for Sample Problem 12.10 88