1. Chapter 5 Chemical Quantities and Reactions
5.1
The Mole

2. Counting Units Counting units
A counting term states a specific number of items.
1 dozen eggs = 12 eggs
1 case soda = 24 cans
1 ream = 500 sheets of paper

3. Avogadro's Number
Small particles such as atoms, molecules, and ions are
counted using the mole.
1 mole = 6.02 x 1023 items
Avogadro’s number
= 6.02 x 1023

4. Mole of Atoms 1 mole of an element = 6.02 x 1023 atoms of that element
1 mole of carbon = 6.02 x 1023 atoms of carbon
1 mole of sodium = 6.02 x 1023 atoms of sodium

5. Number of Particles in One-Mole Samples

6. Avogadro's Number Avogadro’s number, 6.02 x 1023, can be written as an
equality and as two conversion factors.
Equality:
1 mole = x 1023 particles
Conversion Factors:
6.02 x 1023 particles and mole
1 mole x 1023 particles

7. Guide to Calculating Atoms or Molecules

8. Converting Moles to Particles
Avogadro’s number is used to convert moles of a
substance to particles.
How many CO2 molecules are
in 0.50 mole of CO2?
Step 1 State the needed and given quantities:
Given: mole of CO2
Needed: molecules of CO2

9. Converting Moles to Particles
Step 2 Write a plan to convert moles to atoms or molecules:
Avogadro’s number
moles of CO molecules of CO2
Step 3 Use Avogadro’s number to write conversion factors.
1 mole of CO2 = 6.02 x 1023 molecules of CO2
6.02 x 1023 CO2 molecules and mole CO2
 1 mole CO x 1023 CO2 molecules

10. Converting Moles to Particles
Step 4 Set up the problem to calculate the number of particles.
0.50 mole CO2 x x 1023 molecules CO2
1 mole CO2
= 3.01 x 1023 molecules of CO2

11. Learning Check The number of atoms in 2.0 mole of Al atoms is:
A Al atoms
B x 1023 Al atoms
C x 1024 Al atoms

12. Solution The number of atoms in 2.0 moles of Al atoms is:
Step 1 State the needed and given quantities:
Given: mole Al
Needed: atoms of Al
Step 2 Write a plan to convert moles to atoms or molecules:
Avogadro’s number
Moles of Al Atoms of Al

13. Solution The number of atoms in 2.0 moles of Al atoms is:
Step 3 Use Avogadro’s number to write conversion factors.
1 mole of Al = 6.02 x 1023 atoms of Al
6.02 x 1023 atoms Al and mole A
1 mole Al x 1023 atoms Al

14. Solution The number of atoms in 2.0 moles of Al atoms is:
Step 4 Set up the problem to calculate the number
of particles.
C moles Al x x 1023 Al atoms
1 mole Al
= 1.2 x 1024 Al atoms

15. Learning Check The number of moles of S in 1.8 x 1024 atoms of S is:
A mole of S atoms
B moles of S atoms
C x 1048 moles of S atoms

16. Solution The number of moles of S in 1.8 x 1024 atoms of S is:
Step 1 State the needed and given quantities:
Given: x 1024 atoms of S
Needed: moles of S
Step 2 Write a plan to convert moles to atoms or molecules:
Avogadro’s number
Atoms of S Moles of S

17. Solution The number of moles of S in 1.8 x 1024 atoms of S is:
Step 3 Use Avogadro’s number to write conversion factors.
1 mole S = 6.02 x 1023 atoms of S
6.02 x 1023 atoms S and mole S
1 mole S x 1023 atoms S

18. Solution The number of moles of S in 1.8 x 1024 atoms of S is:
Step 4 Set up the problem to calculate the number of particles.
B. 1.8 x 1024 S atoms x mole S
6.02 x 1023 S atoms
= 3.0 moles of S atoms

19. Moles of Elements in a Formula

20. Moles of Elements in a Formula
The subscripts in a formula show:
the relationship of atoms in the formula
the moles of each element in 1 mole of compound
Aspirin
C9H8O4
1 molecule: 9 atoms of C 8 atoms of H atoms of O
1 mole: moles of C 8 moles of H moles of O

21. Moles of Elements in a Formula
Subscripts are used to write conversion factors for
moles of each element in 1 mole of a compound. For
aspirin, C9H8O4, the possible conversion factors are:
9 moles C moles H moles O
1 mole C9H8O mole C9H8O mole C9H8O4
9 moles C moles H moles O

22. Learning Check
How many atoms of O are in mole of aspirin, C9H8O4?

23. Solution Step 1 State the needed and given quantities:
Given: mole of C9H8O4
Need: molecules of C9H8O4
Step 2 Write a plan to convert moles to atoms or molecules:
Moles of aspirin Moles of O Atoms of O

24. Solution Step 3 Use Avogadro’s number to write conversion factors.
Subscript factor: 1 mole of C9H8O4 = 4 moles of O
1 mole C9H8O and moles O
4 moles O mole C9H8O4
Avogadro’s number:
1 mole of O = 6.02 x 1023 atoms of O
1 mole O and x 1023 atoms O
6.02 x 1023 atoms O mole O

25. Solution
Step 4 Set up the problem to calculate the number of particles.
0.150 mole C9H8O4 x 4 mole O x x 1023 atoms O
1 mole C9H8O mole O
= x 1023 atoms of O

26. Chapter 5 Chemical Quantities and Reactions
5.2
Molar Mass

27. Molar Mass The molar mass is the mass of 1 mole of an element
is the atomic mass expressed in grams

28. Molar Mass from Periodic Table
Molar mass is the atomic mass expressed in grams.
1 mole of Ag mole of C mole of S
= g of Ag = 12.0 g of C = 32.1 g of S

29. Learning Check
Give the molar mass for each element (to the tenths place).
A. 1 mole of K atoms = ________
B. 1 mole of Sn atoms = ________
C. 1 mole of Ca atoms = ________

30. Solution Give the molar mass for each element (to the tenths place).
A. 1 mole of K atoms = g of K
B. 1 mole of Sn atoms = g of Sn
C. 1 mole of Ca atoms = g of Ca

31. Guide to Calculating Molar Mass

32. Molar Mass of the Compound C2H6O
To calculate the molar mass of C2H6O:
Step 1 Obtain the molar mass of each element.
1 mole of C = g of C
1 mole of H = g of H
1 mole of O = g of O

33. Molar Mass of the Compound C2H6O
Step 2 Multiply each molar mass by the number of moles (subscripts) in the formula.
2 moles C x g C = g of C
1 mole C
6 moles H x g H = g of H
1 mole H
1 mole O x g O = g of O
1 mole O

34. Molar Mass of the Compound C2H6O
Step 3 Calculate the molar mass by adding the masses of the elements.
2 moles of C = g of C
6 moles of H = g of H
1 mole of O = g of O
Molar mass of C2H6O = g of C2H6O

35. One-Mole Quantities

36. Learning Check What is the molar mass of each compound? A. K2O
B. Al(OH)3

37. Solution What is the molar mass of each compound?
Step 1 Obtain the molar mass of each element.
A. K2O K = 39.1 g/mole
O = 16.0 g/mole
B. Al(OH)3 Al = 27.0 g/mole
O = 16.0 g/mole
H = 1.01 g/mole

38. Solution What is the molar mass of each compound?
Step 2 Multiply each molar mass by the number of moles
(subscripts) in the formula.
A. K2O
2 moles K x g K = g of K
1 mole K
1 mole O x g O = g of O
1 mole O

39. Solution What is the molar mass of each compound?
Step 2 Multiply each molar mass by the number of moles
(subscripts) in the formula.
B. Al(OH)3
1 mole Al x g Al = 27.0 g of Al
1 mole Al
3 moles O x g O = 48.0 g of O
1 mole O
3 moles H x g H = g of H
1 mole H

40. Solution What is the molar mass of each compound?
Step 3 Calculate the molar mass by adding the masses of the elements.
A. K2O 2 moles of K = g of C
1 mole of O = g of O
Molar mass of K2O = g of K2O
B. Al(OH)3 1 mole of Al = g of Al
3 moles of O = g of O
3 moles of H = g of H Molar mass of Al(OH)3 = g of Al(OH)3

41. Learning Check
Prozac, C17H18F3NO, is an antidepressant that inhibits the
uptake of serotonin by the brain. What is the molar mass
of Prozac?
A g/mole
B g/mole
C g/mole

42. Solution Step 1 Obtain the molar mass of each element.
1 mole of C = g of C
1 mole of H = g of H
1 mole of F = g of F
1 mole of N = g of N
1 mole of O = g of O

43. Solution
Step 2 Multiply each molar mass by the number of moles (subscripts) in the formula.
17 moles C x g = g of C
1 mole C
18 moles H x g = g of H
1 mole H
3 moles F x g = g of F
1 mole F
1 mole N x g = g of N
1 mole N
1 mole O x g = g of O
1 mole O

44. Solution
Step 3 Calculate the molar mass by adding the masses of the elements:
1 mole of C17H18F3NO = 309 g of C17H18F3NO

45. Calculations Using Molar Mass
Molar mass conversion factors
are fractions (ratios) written from the molar mass.
relate grams and moles of an element or compound.
for methane, CH4, used in gas stoves and gas heaters, is
1 mole of CH4 = 16.0 g of CH4 (molar mass equality)
Conversion factors:
16.0 g CH and mole CH4
1 mole CH g CH4

46. Guide to Calculating Moles from Mass

47. Converting Mass to Moles of Compound NaCl
A box of table salt, NaCl, contains 737 g of NaCl.
How many moles of NaCl are in the box?

48. Converting Mass to Moles of Compound NaCl
A box of table salt, NaCl, contains 737 g of NaCl.
How many moles of NaCl are in the box?
Step 1 State the given and needed quantities.
Given: g of NaCl
Need: moles of NaCl
Step 2 Write a plan to convert grams to moles.
molar mass
Grams of NaCl Moles of NaCl

49. Converting Mass to Moles of Compound NaCl
Step 3 Determine the molar mass and write conversion factors.
Molar Mass
1 mole Na x g Na = 23.0 g of Na
1 mole Na
1 mole Cl x g Cl = 35.5 g of Cl
1 mole Cl g of NaCl
Conversion Factors
1 mole of NaCl = g of NaCl
58.5 g NaCl and 1 mole NaCl
1 mole NaCl g NaCl

50. Converting Mass to Moles of Compound NaCl
Step 4 Set up the problem to convert grams to moles.
737 g NaCl x 1 mole NaCl = moles of NaCl
58.5 g NaCl

51. Map: Mass – Moles – Particles

52. Learning Check Allyl sulfide, C6H10S, is a compound that has
the odor of garlic. How many moles of
C6H10S are in 225 g?

53. Solution Step 1 State the given and needed quantities.
Given: g of C6H10S
Need: moles of C6H10S
Step 2 Write a plan to convert grams to moles.
molar mass
Grams of C6H10S Moles of C6H10S

54. Solution Step 3 Determine the molar mass and write conversion factors.
6 moles C x g C = g of C
1 mole C
10 moles H x g H = g of H
1 mole H
1 mole S x g S = g of S
1 mole S
= g of C6H10S

55. Solution Step 3 Determine the molar mass and write conversion factors.
1 mole of C6H10S = g of C6H10S
114.2 g C6H10S and 1 mole C6H10S
1 mole C6H10S g C6H10S
Step 4 Set up the problem to convert grams to moles.
225 g C6H10S x 1 mole C6H10S
114.2 g C6H10S
= 19.7 moles of C6H10S

56. Chapter 5 Chemical Quantities and Reactions
5.3
Chemical Reactions and Equations

57. Chemical Changes A chemical change
occurs when a substance is converted into one or more substances with different formulas and different properties
may be observed by the formation of bubbles, a change in color, or production of a solid

58. Visible Evidence of a Chemical Reaction

59. Learning Check Which of the following represent a chemical change?
A. burning a candle
B. ice melting
C. toast burns
D. water turns to steam

60. Solution Which of the following represent a chemical change?
A. burning a candle chemical change
B. ice melting
C. toast burns chemical change
D. water turns to steam

61. Writing a Chemical Equation

62. Symbols Used in Chemical Equations
To write a chemical equation
an arrow indicates reactants form products
reactants are written on the left side of the arrow
products are written on the right side of the arrow
multiple reactants or products are separated by a + sign
the delta {Δ} sign indicates that heat is used to start the reaction

63. Symbols Used in Chemical Equations

64. Identifying a Balanced Equation
In a balanced
chemical equation,
no atoms are lost or gained
the number of reacting atoms is equal to the number of product atoms

65. Balancing a Chemical Equation

66. Balancing a Chemical Equation: Formation of Al2S3
Step 1 Write an equation using the correct formulas of the reactants
and products.
Al(s) S(s) Al2S3(s)
Step 2 Count the atoms of each element in the reactants and products.
Reactants
Products
1 atom Al
2 atoms Al Not balanced
1 atoms S
3 atoms S Not balanced

67. Balancing a Chemical Equation: Formation of Al2S3
Step 3 Use coefficients to balance each element. Starting with the most complex formula, change coefficients to balance equation.
2Al(s) S(s) Al2S3(s)
Step 4 Check the final equation to confirm it is balanced. Make sure coefficients are the lowest ratio.
Reactants
Products
2 atoms Al
2 atoms Al Balanced
3 atoms S
3 atoms S Balanced

68. Learning Check State the number of atoms of each element on the
reactant side and the product side for each of the
following balanced equations.
A. P4(s) + 6Br2(l) PBr3(g)
B. 2Al(s) + Fe2O3(s) Fe(s) + Al2O3(s)

69. Solution State the number of atoms of each element on the reactant
side and the product side for each of the following balanced
equations.
A. P4(s) + 6Br2(l) PBr3(g)
Reactants
Products
P atoms 4
Br atoms 12

70. Solution State the number of atoms of each element on the reactant
side and the product side for each of the following balanced
equations.
B. 2Al(s) + Fe2O3(s) Fe(s) + Al2O3(s)
Reactants
Products
Al atoms 2
Fe atoms
O atoms 3

71. Learning Check Balance the following equation,
Fe3O4(s) + H2(g) Fe(s) + H2O(l)
Reactants
Products
Atoms Fe
Atoms O
Atoms H

72. Solution Balance the following equation,
Fe3O4(s) + H2(g) Fe(s) + H2O(l)
Step 1 Write an equation using the correct formulas of the reactants and products.
Fe3O4(s) + H2(g) Fe(s) + H2O(l)

73. Solution
Step 2 Count the atoms of each element in the reactants and products.
Fe3O4(s) + H2(g) Fe(s) + H2O(l)
Reactants
Products
Atoms Fe 3 1
Atoms O 4
Atoms H 2

74. Solution Step 3 Use Coefficients to balance each element.
Fe3O4(s) + 6H2(g) Fe(s) + 3H2O(l)
Step 4 Check the final equation to confirm it is balanced.
Reactants
Products
Atoms Fe 3 1
Atoms O 4
Atoms H 2

75. Balancing Equations with Polyatomic Ions

76. Balancing Equations with Polyatomic Ions
When balancing equations with polyatomic ions, balance each
polyatomic ion as a unit.
2Na3PO4(aq) + 3MgCl2(aq) Mg3(PO4)2(s) + 6NaCl(aq)
Reactants
Products
PO43− ions 2
Na+ ions 6
Mg2+ ions 3
Cl− ions

77. Learning Check
Balance and list the coefficients from reactants to products.
A. __Fe2O3(s) __C(s) __Fe(s) __CO2(g)
1) 2, 3, 2, ) 2, 3, 4, ) 1, 1, 2, 3
B. __Al(s) + __FeO(s) __Fe(s) __Al2O3(s)
1) 2, 3, 3, ) 2, 1, 1, ) 3, 3, 3, 1
C. __Al(s) + __H2SO4(aq) __Al2(SO4)3(aq) + __H2(g)
1) 3, 2, 1, ) 2, 3, 1, ) 2, 3, 2, 3

78. Solution A. 2) 2, 3, 4, 3 2Fe2O3(s) + 3C(s) 4Fe(s) + 3CO2(g)
B. 1) 2, 3, 3, 1
2Al(s) + 3FeO(s) Fe(s) + 1Al2O3(s)
C. 2) 2, 3, 1, 3
2Al(s) + 3H2SO4(aq) Al2(SO4)3(aq) + 3H2(g)

79. Chapter 5 Chemical Quantities and Reactions
5.4
Types of Reactions

80. Types of Reactions Chemical reactions can be classified as
combination reactions
decomposition reactions
single replacement reactions
double replacement reactions
combustion reactions

81. Combination Reactions
In a combination reaction,
two or more elements form one product
or simple compounds combine to form one product
2Mg(s) + O2(g) MgO(s)
2Na(s) + Cl2(g) NaCl(s)
SO3(g) + H2O(l) H2SO4(aq)

82. Combination Reaction: MgO

83. Decomposition Reaction
In a decomposition reaction, one substance splits into
two or more simpler substances.
2HgO(s) Hg(l) + O2(g)
2KClO3(s) KCl(s) + 3O2(g)

84. Decomposition Reaction: HgO

85. Single Replacement Reaction
In a single replacement reaction, one element takes the
place of a different element in another reacting a compound.
Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s)

86. Single Replacement Reaction: ZnCl2

87. Double Replacement Reaction
In a double replacement, two elements in the reactants
exchange places.
AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
ZnS(s) HCl(aq) ZnCl2(aq) + H2S(g)

88. Double Replacement Reaction: BaSO4

89. Combustion Reaction In a combustion reaction,
a carbon-containing compound burns in oxygen gas to form carbon dioxide (CO2) and water (H2O)
energy is released as a product in the form of heat
CH4(g) + 2O2(g) CO2(g) + 2H2O(g) + energy

90. Combustion Reaction
Insert diagram of following balanced reaction with triangle over the reaction arrow.
C3H8(g) + 5O2(g) Δ 3CO2(g) + 4H2O(g)

91. Summary of Reaction Types

92. Learning Check
Classify each of the following reactions as combination,
decomposition, single replacement, double replacement, or
combustion.
A. 2Al(s) + 3H2SO4(aq) Al2(SO4)3(s) + 3H2(g)
B. Na2SO4(aq) + 2AgNO3(aq) Ag2SO4(s) + 2NaNO3(aq)
C. 3C(s) + Fe2O3(s) Fe(s) + 3CO(g)
D. C2H4(g) + 2O2(g) CO2(g) + 2H2O(g)

93. Solution A. 2Al(s) + 3H2SO4(aq) Al2(SO4)3(s) + 3H2(g)
Single Replacement
B. Na2SO4(aq) + 2AgNO3(aq) Ag2SO4(s) + 2NaNO3(aq)
Double Replacement
C. N2(g) + O2(g) NO(g) Combination
D. C2H4(g) + 2O2(g) CO2(g) + 2H2O(g)
Combustion

94. Learning Check Identify each reaction as combination, decomposition,
combustion, single replacement, or double replacement.
A. 3Ba(s) + N2(g) Ba3N2(s)
B. 2Ag(s) + H2S(aq) Ag2S(s) + H2(g)
C. 2C2H6(g) + 7O2(g) CO2(g) + 6H2O(g)
D. PbCl2(aq) + K2SO4(aq) KCl(aq) + PbSO4(s)
E. K2CO3(s) K2O(aq) + CO2(g)

95. Solution Identify each reaction as combination, decomposition,
combustion, single replacement, or double replacement.
A. 3Ba(s) + N2(g) Ba3N2(s) Combination
B. 2Ag(s) + H2S(aq) Ag2S(s) + H2(g)
Single Replacement
C. C2H6(g) + 7O2(g) CO2(g) + 6H2O(g)
Combustion

96. Solution Identify each reaction as combination, decomposition,
combustion, single replacement, or double replacement.
D. PbCl2(aq) + K2SO4(aq) KCl(aq) + PbSO4(s)
Double Replacement
E. K2CO3(s) K2O(aq) + CO2(g) Decomposition

97. Chapter 5 Chemical Quantities and Reactions
5.5
Oxidation−Reduction Reactions

98. Oxidation−Reduction Reactions
An oxidation–reduction reaction
provides us with energy from food
provides electrical energy in batteries
occurs when iron rusts:
4Fe(s) + 3O2(g) Fe2O3(s)

99. Oxidation−Reduction In an oxidation–reduction reaction, electrons are
transferred from one substance to another.

100. Oxidation−Reduction
Reduced Oxidized

101. Oxidation and Reduction
2Cu(s) + O2(g) CuO
OIL RIG
Oxidation is loss of electrons.
2Cu(s) Cu2+(s) + 4e−
Reduction is gain of electrons.
O2(g) + 4e− O2− (s)
The green patina on copper is due to oxidation

102. Zn replaces Cu2+

103. Zn Transfers Electrons to Cu2+
OIL Oxidation is losing electrons.
RIG Reduction is gaining electrons.

104. Learning Check
Identify each of the following as oxidation or reduction:
__A. Sn(s) Sn4+(aq) + 4e−
__B. Fe3+(aq) + 1e− Fe2+(aq)
__C. Cl2(g) + 2e− Cl− (aq)

105. Solution Identify each of the following as oxidation or reduction:
Oxidation __A. Sn(s) Sn4+(aq) + 4e−
Reduction __B. Fe3+(aq) + 1e− Fe2+(aq)
Reduction __C. Cl2(g) + 2e− Cl− (aq)

106. Learning Check In light-sensitive sunglasses, UV light initiates an
oxidation–reduction reaction.
UV light
2Ag Cl− Ag + Cl2
A. Which reactant is oxidized?
B. Which reactant is reduced?

107. Solution In light-sensitive sunglasses, UV light initiates an
oxidation-reduction reaction.
uv light
2Ag Cl− Ag + Cl2
A. Which reactant is oxidized? 2Cl− Cl e−
B. Which reactant is reduced? 2Ag e− Ag

108. Oxidation–Reduction in Biological Systems
The oxidation of a typical biochemical molecule can
involve the transfer of two hydrogen atoms (or 2H+ and
2e−) to a proton acceptor such as the coenzyme FAD (flavin
adenine dinucleotide).

109. Characteristics of Oxidation and Reduction

110. Characteristics of Oxidation and Reduction
Methyl alcohol formaldehyde Oxidation (loss of H as
hydrogen gas)
CH3OH H2CO + 2H2
Formaldehyde formic acid
2H2CO + O H2CO Oxidation (addition of O)

111. Chapter 5 Chemical Quantities and Reactions
5.6
Mole Relationships in Chemical Equations

112. Law of Conservation of Mass
The law of conservation of mass indicates that in an
ordinary chemical reaction,
matter cannot be created or destroyed
no change in total mass occurs
the mass of products is equal to mass of reactants

113. Conservation of Mass

114. Information from a Balanced Equation

115. Reading Equations in Moles
Consider the following equation:
2Fe(s) S(s) Fe2S3(s)
This equation can be read in “moles” by placing the
word “moles of” between each coefficient and formula.
2 moles of Fe + 3 moles of S mole of Fe2S3

116. Writing Conversion Factors from Equations
A mole–mole factor is a ratio of the moles for any two
substances in an equation.
2Fe(s) + 3S(s) Fe2S3(s)
Fe and S moles Fe and moles S
3 moles S moles Fe
Fe and Fe2S moles Fe and moles Fe2S3
1 mole Fe2S moles Fe
S and Fe2S moles S and mole Fe2S3
1 mole Fe2S moles S

117. Learning Check Consider the following equation: 3H2(g) + N2(g) 2NH3(g)
A. A mole–mole factor for H2 and N2 is:
1) 3 moles N ) 1 mole N ) 1 mole N2
1 mole H moles H moles H2
B. A mole–mole factor for NH3 and H2 is:
1) 1 mole H ) 2 moles NH ) 3 moles N2
2 moles NH moles H moles NH3

118. Solution 3H2(g) + N2(g) 2NH3(g)
A. A mole–mole factor for H2 and N2 is:
2) 1 mole N2
3 moles H2
B. A mole–mole factor for NH3 and H2 is:
2) 2 moles NH3

119. Calculations with Mole Factors
How many moles of Fe2O3 can form from 6.0 moles of O2?
4Fe(s) + 3O2(g) Fe2O3(s)
Relationship: 3 moles of O2 = 2 moles of Fe2O3
Use a mole–mole factor to determine the moles of Fe2O3.
6.0 moles O2 x 2 moles Fe2O3 = moles of Fe2O3
3 moles O2

120. Guide to Using Mole–Mole Factors

121. Learning Check How many moles of Fe are needed for the reaction of
12.0 moles of O2?
4Fe(s) + 3O2(g) Fe2O3(s)
A moles of Fe
B moles of Fe
C moles of Fe

122. Solution In a problem, identify the compounds given and needed.
How many moles of Fe are needed for the reaction of
12.0 moles of O2?
4Fe(s) + 3O2(g) Fe2O3(s)
Step 1 State the given and needed quantities.
Given: moles of O2 Needed: ? moles of Fe
The possible mole factors for the solution are:
4 moles Fe and 3 moles O2
3 moles O2 4 moles Fe

123. Solution
Step 2 Write a plan to convert the given to the needed moles. Mole–mole factor
Moles of O Moles of Fe
Step 3 Use coefficients to write relationships and mole–mole factors.
4 moles of Fe = moles of O2
4 moles Fe and 3 moles O2
3 moles O moles Fe

124. Solution
Step 4 Set up the problem using the mole–mole factor that cancels given moles.
12.0 moles O2 x 4 moles Fe = moles of Fe
3 moles O2
The answer is C, 16.0 moles of Fe.

125. Chapter 5 Chemical Quantities and Reactions
5.7
Mass Calculations for Reactions

126. Mass Calculations in Equations

127. Moles to Grams Suppose we want to determine the mass (g) of NH3 that
can be produced from 32 grams of N2.
N2(g) + 3H2(g) NH3(g)
Step 1 Use molar mass to convert grams of given to moles.
1 mole of N2 = g of N2
1 mole N and g N2
28.0 g N mole N2
32 g N2 x 1 mole N2 = mole of N2
28.0 g N2

128. Moles to Grams
Step 2 Write a mole–mole factor from the coefficients in the equation.
1 mole of N2 = 2 moles of NH3
1 mole N and 2 moles NH3
2 moles NH mole N2

129. Moles to Grams
Step 3 Convert moles of given to moles of needed using the mole–mole factor.
1.1 mole N2 x 2 moles NH3 = 2.2 moles of NH3
1 mole N2

130. Moles to Grams
Step 4 Convert moles of needed substance to grams using molar mass.
1 mole of NH3 = g of NH3
1 mole NH3 and g NH3
17.0 g NH mole NH3
2.2 moles NH3 x g NH3 = 37 g of NH3
1 mole NH3

131. Learning Check
How many grams of O2 are needed to produce 45.8 grams of
Fe2O3 in the following reaction?
4Fe(s) + 3O2(g) Fe2O3(s)
A g of O2
B g of O2
C g of O2

132. Solution How many grams of O2 are needed to produce 45.8 grams of
Fe2O3 in the following reaction?
4Fe(s) + 3O2(g) Fe2O3(s)
Step 1 Use molar mass to convert grams of given to moles.
1 mole of Fe2O3 = g of Fe2O3
1 mole Fe2O and g Fe2O3
159.7 g Fe2O mole Fe2O3
45.8 g Fe2O3 x 1 mole Fe2O3 = mole of Fe2O3
159.7 g Fe2O3

133. Solution
Step 2 Write a mole–mole factor from the coefficients in the equation.
3 moles of O2 = 2 moles of Fe2O3
3 moles O and moles Fe2O3
2 moles Fe2O moles O2
Step 3 Convert moles of given to moles of needed using the mole–mole factor.
0.287 mole Fe2O3 x 3 moles O = mole of O2
2 moles Fe2O3

134. Solution
Step 4 Convert moles of needed substance to grams using molar mass.
1 mole of O2 = g of O2
1 mole O2 and g O2
32.0 gO mole O2
0.430 mole O2 x g O2 = g of O2
1 mole O2
The answer is B, 13.8 g of O2.

135. Learning Check
The reaction between H2 and O2 produces 13.1 g of water.
How many grams of O2 reacted?
2H2(g) O2(g) H2O(g)
? g g

136. Solution 2H2(g) + O2(g) 2H2O(g) ? g 13.1 g
Step 1 Use molar mass to convert grams of given to moles.
1 mole of H2O = g of H2O
1 mole H2O and g H2O
18.0 g H2O mole H2O
13.1 g H2O x 1 mole H2O = mole of H2O
18.0 g H2O

137. Solution
Step 2 Write a mole–mole factor from the coefficients in the equation.
2 moles of H2O = 1 mole of O2
2 moles H2O and mole O2_
1 moles O moles H2O
Step 3 Convert moles of given to moles of needed using the mole–mole factor.
0.728 mole H2O x 1 mole O2 = mole of O2
2 moles H2O

138. Solution
Step 4 Convert moles of needed substance to grams using molar mass.
1 mole of O2 = g of O2
0.364 mole O2 x g O2 = g of O2
1 mole O2

139. Chapter 5 Chemical Quantities and Reactions
5.8
Energy in Chemical Reactions

140. Molecules Must Collide for Reaction
Three conditions for a reaction to occur are:
1. collision: The reactants must collide.
2. orientation: The reactants must align properly to
break and form bonds.
3. energy: The collision must provide the energy of
activation.

141. Exothermic Reaction In an exothermic reaction, heat is released
the energy of the products is less than the energy of the reactants
heat is a product
C(s) + 2H2(g) CH4(g) + 18 kcal

142. Endothermic Reactions
In an endothermic reaction,
heat is absorbed
the energy of the products is greater than the energy of the reactants
heat is a reactant (added)
N2(g) + O2(g) kcal  2NO(g)

143. Learning Check Identify each reaction as exothermic or endothermic.
A. N2(g) + 3H2(g) NH3(g) kcal
B. CaCO3(s) kcal CaO(s) + CO2(g)
C. 2SO2(g) + O2(g) SO3(g) + heat

144. Solution Identify each reaction as exothermic or endothermic.
A. N2(g) + 3H2(g) NH3(g) kcal Exothermic
B. CaCO3(s) kcal CaO(s) + CO2(g)
Endothermic
C. 2SO2(g) + O2(g) SO3(g) + heat
Exothermic

145. Reaction Rate The reaction rate
is the speed at which reactant is used up
is the speed at which product forms
increases when temperature rises because reacting molecules move faster, providing more colliding molecules with energy of activation
increases with increase in concentration of reactants

146. Catalyst A catalyst increases the rate of a reaction
lowers the energy of activation
is not used up during the reaction

147. Factors That Increase Reaction Rate

148. Learning Check State the effect of each on the rate of reaction as
increases, decreases, or has no effect:
A. increasing the temperature
B. removing some of the reactants
C. adding a catalyst
D. placing the reaction flask in ice
E. increasing the concentration of one of the reactants

149. Solution State the effect of each on the rate of reaction as
increases, decreases, or has no effect:
A. increasing the temperature increases
B. removing some of the reactants decreases
C. adding a catalyst increases
D. placing the reaction flask in ice decreases
E. increasing the concentration of one of the reactant
increases

150. Learning Check
Indicate the effect of each factor listed on the rate of the
following reaction as increases, decreases, or no change.
2CO(g) + O2(g) CO2(g)
A. raising the temperature
B. adding O2
C. adding a catalyst
D. lowering the temperature

151. Solution Indicate the effect of each factor listed on the rate of the
following reaction as increases, decreases, or no change.
2CO(g) + O2(g) CO2(g)
A. raising the temperature increases
B. adding O2 increases
C. adding a catalyst increases
D. lowering the temperature decreases

152. Chemical Quantities and Reactions