1. 4.1 – Writing and Balancing Chemical Equations — The Magic of Chemistry

2. Balancing Chemical Equations, p. 164
Chemical equations need to be balanced in order to maintain the conservation laws

3. Balancing Chemical Equations, p. 164
Law of conservation of mass
In a closed system, the total mass does not change
The mass of the products equals the mass of the reactants

4. Balancing Chemical Equations, p. 164
A balanced chemical equation must ensure the conservation of mass, atoms and electrical charges

5. Balancing Chemical Equations, p. 164
Coefficients
Numbers written before the formula of each reactant and product representing how many particles of each are present
Apply to or multiple every element and atom in the particle, not just the first

6. H2S PbCl2  PbS HCl
H = 2
H = 1
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

7. H2S PbCl2  PbS HCl
H = 2
H = 1
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

8. H2S PbCl2  PbS HCl
H = 2
H = 1
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

9. H2S PbCl2  PbS HCl
H = 2
H = 1
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

10. H2S PbCl2  PbS HCl
H = 2
H = 1
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

11. H2S PbCl2  PbS HCl 2
H = 2
H = 1
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

12. H2S PbCl2  PbS HCl 2
H = 2
H = 2
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 1

13. H2S PbCl2  PbS HCl 2
H = 2
H = 2
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 2

14. H2S PbCl2  PbS HCl 2
H = 2
H = 2
S = 1
S = 1
Pb = 1
Pb = 1
Cl = 2
Cl = 2

15. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

16. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

17. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

18. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

19. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

20. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

21. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

22. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 1
Na = 3

23. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 5
O = 5
Na = 3
Na = 3

24. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 13
H = 5
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

25. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 15
H = 5
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

26. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 15
H = 5
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

27. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O1
H = 15
H = 5
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

28. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 5
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

29. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 11
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

30. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 11
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

31. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 11
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

32. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 11
P = 1
P = 1
O = 7
O = 5
Na = 3
Na = 3

33. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 15
P = 1
P = 1
O = 7
O = 7
Na = 3
Na = 3

34. (NH4)3PO4 + NaOH  Na3PO4 + NH3 + H2O15
H = 15
P = 1
P = 1
O = 7
O = 7
Na = 3
Na = 3

35. C19H17NO O2  CO H2O N2
C = 19
C = 1
H = 17
H = 2
N = 1
N = 2
O = 5
O = 3

36. C19H17NO O2  CO H2O N2
C = 19
C = 1
H = 17
H = 2
N = 1
N = 2
O = 5
O = 3

37. C19H17NO O2  CO H2O N2 2
C = 19
C = 1
H = 17
H = 2
N = 1
N = 2
O = 5
O = 3

38. C19H17NO O2  CO H2O N2 2
C = 19
C = 1
H = 17
H = 2
N = 2
N = 2
O = 5
O = 3

39. C19H17NO O2  CO H2O N2 2
C = 38
C = 1
H = 34
H = 2
N = 2
N = 2
O = 8
O = 3

40. C19H17NO O2  CO H2O N2 2
C = 38
C = 1
H = 34
H = 2
N = 2
N = 2
O = 8
O = 3

41. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 1
H = 34
H = 2
N = 2
N = 2
O = 8
O = 3

42. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 3

43. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 77

44. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 77

45. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 77

46. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 77

47. C19H17NO O2  CO H2O N2 2 38
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 77

48. C19H17NO O2  CO H2O N2 2 38 17
C = 38
C = 38
H = 34
H = 2
N = 2
N = 2
O = 8
O = 77

49. C19H17NO O2  CO H2O N2 2 38 17
C = 38
C = 38
H = 34
H = 34
N = 2
N = 2
O = 8
O = 77

50. C19H17NO O2  CO H2O N2 2 38 17
C = 38
C = 38
H = 34
H = 34
N = 2
N = 2
O = 8
O = 93

51. C19H17NO O2  CO H2O N2 2 38 17
C = 38
C = 38
H = 34
H = 34
N = 2
N = 2
O = 8
O = 93

52. can only add an even amount
C19H17NO O2  CO H2O N2 2 38 17
can only add an even amount
C = 38
C = 38
H = 34
H = 34
N = 2
N = 2
O = 8
O = 93
need an odd number

53. Balancing Chemical Equations, p. 164
If you need an odd amount of a diatomic element, doubling everything else will produce a need for an even amount

54. C19H17NO O2  CO H2O N2 2 38 17
C = 38
C = 38
H = 34
H = 34
N = 2
N = 2
O = 8
O = 93

55. C19H17NO O2  CO H2O N2 4 76 34 2
C = 38
C = 38
H = 34
H = 34
N = 2
N = 2
O = 8
O = 93

56. C19H17NO O2  CO H2O N2 4 87 76 34 2
C = 76
C = 76
H = 68
H = 68
N = 4
N = 4
O = 14
O =
186

57. C19H17NO O2  CO H2O N2 4 87 76 34 2
C = 76
C = 76
H = 68
H = 68
N = 4
N = 4
O =
186
O =
186

58. C19H17NO O2  CO H2O N2 4 87 76 34 2
C = 76
C = 76
H = 68
H = 68
N = 4
N = 4
O =
186
O =
186

59. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I21
S = 3
S = 1
O = 16
O = 7
K = 2
K = 2
I = 2
I = 2
H = 2
H = 3

60. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I21
S = 3
S = 1
O = 16
O = 7
K = 2
K = 2
I = 2
I = 2
H = 2
H = 3

61. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I21
S = 3
S = 1
O = 16
O = 7
K = 2
K = 2
I = 2
I = 2
H = 2
H = 3

62. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I21
O = 16
O = 10
K = 2
K = 2
I = 2
I = 2
H = 2
H = 6

63. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I21
O = 16
O = 10
K = 2
K = 2
I = 2
I = 2
H = 2
H = 6

64. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I21
O = 16
O = 10
K = 2
K = 2
I = 2
I = 2
H = 2
H = 6

65. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I216
O = 18
K = 2
K = 6
I = 2
I = 2
H = 2
H = 6

66. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I216
O = 18
K = 2
K = 6
I = 2
I = 2
H = 2
H = 6

67. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I216
O = 18
K = 2
K = 6
I = 2
I = 2
H = 2
H = 6

68. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I216
O = 18
K = 2
K = 6
I = 2
I = 2
H = 2
H = 6

69. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I216
O = 18
K = 2
K = 6
I = 2
I = 2
H = 2
H = 6

70. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 2 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 16
O = 18
K = 2
K = 6
I = 2
I = 2
H = 2
H = 6

71. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 2 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 16
O = 18
K = 6
K = 6
I = 6
I = 2
H = 2
H = 6

72. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 2 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 16
O = 18
K = 6
K = 6
I = 6
I = 2
H = 2
H = 6

73. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 3 2 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 16
O = 18
K = 6
K = 6
I = 6
I = 2
H = 2
H = 6

74. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 3 2 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 18
O = 18
K = 6
K = 6
I = 6
I = 2
H = 6
H = 6

75. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 3 2 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 18
O = 18
K = 6
K = 6
I = 6
I = 2
H = 6
H = 6

76. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 3 2 3 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 18
O = 18
K = 6
K = 6
I = 6
I = 2
H = 6
H = 6

77. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 3 2 3 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 18
O = 18
K = 6
K = 6
I = 6
I = 6
H = 6
H = 6

78. Cr2(SO4)3 + KI + KIO3 + H2O  Cr(OH)3 + K2SO4 + I25 3 2 3 3
Cr = 2
Cr = 2
S = 3
S = 3
O = 18
O = 18
K = 6
K = 6
I = 6
I = 6
H = 6
H = 6

79. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 1
Cl = 4
Cl = 4
O = 2
O = 1
Ag = 1
Ag = 2

80. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 1
Cl = 4
Cl = 4
O = 2
O = 1
Ag = 1
Ag = 2

81. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 1
Cl = 4
Cl = 4
O = 2
O = 1
Ag = 1
Ag = 2

82. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 1
Cl = 5
Cl = 4
O = 2
O = 1
Ag = 2
Ag = 2

83. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 1
Cl = 5
Cl = 4
O = 2
O = 1
Ag = 2
Ag = 2

84. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 1
Cl = 5
Cl = 4
O = 2
O = 1
Ag = 2
Ag = 2

85. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 2
Cl = 5
Cl = 8
O = 2
O = 1
Ag = 2
Ag = 2

86. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 2
Cl = 5
Cl = 8
O = 2
O = 1
Ag = 2
Ag = 2

87. MoCl3 + O2 + AgCl  MoCl4 + Ag2O1
Mo = 2
Cl = 5
Cl = 8
O = 2
O = 1
Ag = 2
Ag = 2

88. MoCl3 + O2 + AgCl  MoCl4 + Ag2O8
Cl = 8
O = 2
O = 1
Ag = 2
Ag = 2

89. MoCl3 + O2 + AgCl  MoCl4 + Ag2O8
Cl = 8
O = 2
O = 1
Ag = 2
Ag = 2

90. MoCl3 + O2 + AgCl  MoCl4 + Ag2O16
Cl = 16
O = 2
O = 2
Ag = 4
Ag = 4

91. MoCl3 + O2 + AgCl  MoCl4 + Ag2O16
Cl = 16
O = 2
O = 2
Ag = 4
Ag = 4

92. Keeping Your Balance — Helpful Hints, p. 165
Write a properly balanced equation for the following chemical reaction:
Copper(I) oxide and carbon react to form copper and carbon dioxide
2Cu2O + C  4Cu + CO2