Download presentation
Presentation is loading. Please wait.
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
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.