Download Chemical Reaction

General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 6
Chemical Reactions
and Quantities
6.1
Equations for
Chemical Reactions
© 2013 Pearson Education, Inc.
Lectures
Chemical Change
A chemical change occurs
when a substance is
converted into one or more
new substances.
Chemical changes can be
recognized by
 a change in color,
 the formation of a solid, or
 the formation of bubbles.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
A chemical change produces new
substances. When silver (Ag)
reacts with sulfur (S), it produces
silver sulfide (Ag2S).
2
Evidence of Chemical Change
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
3
Chemical Reactions
A chemical reaction
 involves the rearrangement of
atoms.
 produces one or more new
substances.
 can be observed by the
appearance of new physical
properties.
A chemical reaction forms new
products with different properties.
An antacid (NaHCO3) tablet
in water forms bubbles of carbon
dioxide (CO2).
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
4
Writing a Chemical Equation
A chemical equation tells us what substances react
(reactants) and what substances are formed
(products).
C(s) + O2(g)
reactants
CO2(g)
product
(+) used when there is two or more products or reactants
heat is used to start the reaction
(s) the compound is a solid
(l) the compound is a liquid
(g) the compound is a gas
(aq) aqueous, the compound is dissolved in water
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
5
Writing a Chemical Equation
Reaction Description:
In a Bunsen burner, natural gas (methane,
CH4) burns in oxygen, producing carbon
dioxide gas and water vapor.
Skeleton Equation:
Identify the reactants (CH4 and O2) and
products (CO2 and H2O) and write equation:
CH4(g) + O2(g)  CO2(g)
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
+ H2O(g)
6
Equation for a Chemical Reaction
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
7
Law of Conservation of Mass
 Fundamental scientific law, first established in
the late 1790’s by French chemist Antoine
LaVoisier  known as the father of modern
chemistry
 LaVoisier showed that the total mass of the
reactants in a chemical reaction always
equals the total mass of the products
 “For any chemical reaction, the mass of the
reactants always equals the mass of the
products”
8
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
8
Balanced Chemical Equations
In a balanced chemical equation, the number of
atoms in the reactants is equal to the number of atoms
in the products for each element.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
9
Balancing Chemical Equations
To balance a chemical equation,
 whole number coefficients are placed in front of
the chemical formulas.
 coefficients in front of a molecule represent the
multiple of that molecule needed in a balanced
reaction.
 subscripts are never changed.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
10
Checking a Balanced Equation
Reactants
© 2013 Pearson Education, Inc.
Products
Atoms C
1
1
balanced
Atoms H
4
4
Atoms O
4
4
balanced
balanced
Chapter 6, Section 1
11
Guide to Balancing a Chemical
Equation
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
12
Steps to Balancing a Chemical
Equation
Balance the following chemical reaction:
Ethanol (C2H6O) burns in the presence of oxygen
gas(O2) to produce steam (H2O) and carbon dioxide
(CO2) gas.
Step 1 Write an equation using the correct formulas
of the reactants and products.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
13
Steps to Balancing a Chemical
Equation
Step 2 Count the atoms of each element in the
reactants and products.
Reactants Products
© 2013 Pearson Education, Inc.
Atoms of C
2
1
not balanced
Atoms of H
6
2
Atoms of O
3
3
not balanced
balanced
Chapter 6, Section 1
14
Steps to Balancing a Chemical
Equation
Step 3 Use coefficients to balance each element.
Step 4 Check the final equation to confirm it is
balanced.
Create a balance sheet to count atoms of each element.
Reactants Products
© 2013 Pearson Education, Inc.
Atoms of C
2
2
Atoms of H
6
6
Atoms of O
7
7
Chapter 6, Section 1
balanced
balanced
balanced
15
Learning Check
Determine if each equation is balanced or not.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
16
Learning Check
Write a balanced equation for the reaction of nitrogen gas
(N2) with hydrogen gas (H2) to form ammonia gas (NH3).
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
17
Learning Check
Check the balance of atoms in the following equation:
1. number of H atoms in products
A. 2
B. 4
C. 8
2. number of O atoms in reactants
A. 2
B. 4
C. 8
3. number of Fe atoms in reactants
A. 1
© 2013 Pearson Education, Inc.
B. 3
Chapter 6, Section 1
C. 4
18
Equations with Polyatomic Ions
When balancing equations with polyatomic ions that
remain the same on both sides of the equation,
balance them as a unit.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
19
Balancing with Polyatomic Ions
Balance the following chemical equation.
Step 1 Write the equation using the correct formulas
of the reactants and products.
© 2013 Pearson Education, Inc.
Chapter 6, Section 1
20
Balancing with Polyatomic Ions
Balance the following chemical equation.
Step 2 Count the atoms of each element in the
reactants and products.
Reactants Products
© 2013 Pearson Education, Inc.
Atoms of Na
3
1
PO43− ions
1
2
Atoms of Mg 1
3
Atoms of Cl
1
2
Chapter 6, Section 1
not balanced
not balanced
not balanced
not balanced
21
Balancing with Polyatomic Ions
Balance the following chemical equation.
Step 3 Use coefficients to balance each element.
Step 4 Check the final equation to confirm it is
balanced.
Reactants Products
© 2013 Pearson Education, Inc.
Atoms of Na
6
6
PO43− ions
2
2
Atoms of Mg
3
3
Atoms of Cl
6
6
Chapter 6, Section 1
balanced
balanced
balanced
balanced
22
Learning Check
Balance and list the coefficients from reactants to products.
1. __Fe2O3(s) + __C(s)
A. 2, 3, 2,3
B. 2, 3, 4, 3
2. __Al(s) + __FeO(s)
A. 2, 3, 3, 1
__Fe(s) + __CO2(g)
__Fe(s) + __Al2O3(s)
B. 2, 1, 1, 1
3. __Al(s) + __H2SO4(aq)
A. 3, 2, 1, 2
© 2013 Pearson Education, Inc.
C. 1, 1, 2, 3
__Al2(SO4)3(aq) + __H2(g)
B. 2, 3, 1, 3
Chapter 6, Section 1
C. 3, 3, 3, 1
C. 2, 3, 2, 3
23
General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 6
Chemical Reactions
and Quantities
6.2
Types of Reactions
© 2013 Pearson Education, Inc.
Lectures
Types of Reactions
Chemical reactions can be classified as
 combination reactions,
 decomposition reactions,
 single replacement reactions,
 double replacement reactions, or
 combustion reactions.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
25
Combination Reaction
In a combination reaction, two or more elements (or
simple compounds) combine to form one product.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
26
Formation of MgO
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
27
Decomposition Reaction
In a decomposition reaction, one substance splits into
two or more simpler substances.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
28
Decomposition of HgO
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
29
Single Replacement Reaction
In a single replacement reaction, one element takes
the place of a different element in a reacting compound.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
30
Zn and HCl Combine in a Single
Replacement Reaction
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
31
Double Replacement Reaction
In a double replacement reaction, the two positive
ions in the reacting compounds exchange places.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
32
Example of Double Replacement
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
33
Combustion Reaction
In a combustion reaction, a carbon-containing
compound that is the fuel burns in oxygen from the air
to produce carbon dioxide (CO2), water (H2O), and
energy in the form of heat or a flame.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
34
Combustion Reaction
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
35
Summary Reaction Types
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
36
Learning Check
Classify the following reactions as a combination or
decomposition reaction.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
37
Learning Check
Classify each of the following reactions as a single
replacement or a double replacement reaction.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
38
Learning Check
Identify each of the following reactions as a
combination, a decomposition, a single replacement,
a double replacement, or a combustion reaction.
© 2013 Pearson Education, Inc.
Chapter 6, Section 2
39
General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 6
Chemical Reactions
and Quantities
6.3
Oxidation–Reduction
Reactions
© 2013 Pearson Education, Inc.
Lectures
Everyday Oxidation–Reduction
Reactions
In an oxidation–reduction reaction,
 electrons are transferred from one
substance to another.
 if one substance loses electrons,
another substance must gain
electrons.
 energy is provided to us from food.
 electrical energy is provided in
batteries.
 iron rusts.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
41
Transfer of Electrons
In oxidation–reduction reactions,
 the process of losing electrons is called oxidation.
Oxidation Is a Loss of electrons.
(OIL)
 the process of gaining electrons is called reduction.
Reduction Is a Gain of electrons.
(RIG)
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
42
Oxidation and Reduction
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
43
Oxidized or Reduced?
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
44
Oxidation and Reduction,
Formation of CaS
In the reaction:
 the reactant, Ca has a charge of 0 and the
product, CaS contains a Ca2+ ion.
 calcium loses two electrons, meaning oxidation
has taken place.
 the reactant, S has a charge of 0 and the product,
CaS contains an S2− ion.
 sulfur gains two electrons, meaning reduction has
taken place.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
45
Oxidation and Reduction,
Formation of CaS
Adding the two reactions, oxidation and reduction,
gives us the overall reaction.
The overall reaction is written as:
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
46
Zn and Cu2+
When zinc is added to copper(II) sulfate, zinc undergoes
oxidation, while copper undergoes reduction.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
47
Electron Transfer from Zn to Cu2+
Oxidation: electron loss
Reduction: electron gain
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
48
Learning Check
Identify each of the following reactions as oxidation
or reduction.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
49
Learning Check
In light-sensitive sunglasses, UV light initiates an
oxidation-reduction reaction.
1. Which reactant is oxidized?
2. Which reactant is reduced?
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
50
Learning Check
Identify the substances that are oxidized and reduced in
each of the following reactions.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
51
Oxidation–Reduction in Biological
Systems
In biological systems, oxidation may involve
 the loss of H or
 the gain of O.
In biological systems, reduction may involve
 the gain of H or
 the loss of O.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
52
Oxidation–Reduction in Biological
Systems
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
53
Characteristics of Oxidation and
Reduction
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
54
General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 6
Chemical Reactions
and Quantities
6.4
The Mole
Lectures
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
55
Counting Units
Counting terms are used to describe specific quantities.
 1 dozen donuts
= 12 donuts
 1 ream of paper = 500 sheets
 1 case = 24 cans
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
56
A Mole of Atoms
A mole is a counting unit that contains
 the same number of particles as there are carbon
atoms in 12.0 g of carbon 12C.
 6.02 x 1023 atoms of an element (Avogadro’s
number).
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
57
A Mole of Sulfur
1 mole of sulfur contains Avogadro’s number of atoms.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
58
A Mole of a Compound
A mole
 of a covalent compound has Avogadro’s number of
molecules.
 of an ionic compound contains Avogadro’s number of
formula units.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
59
Number of Particles in One Mole
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
60
Avogadro’s Number as an
Equality
Avogadro’s number (6.02 x 1023) can be written as an
equality and two conversion factors.
Equality:
Conversion Factors:
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
61
Guide to Calculating Atoms or
Moles
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
62
Using Avogadro’s Number in
Calculations
How many Cu atoms are in 0.50 mole of Cu?
Step 1 State the given and needed quantities.
Analyze the Problem.
Given
Need
0.50 mole Cu
atoms of Cu
Step 2 Write a plan to convert moles to atoms or
molecules.
moles of Cu Avogadro's number atoms of Cu
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
63
Using Avogadro’s Number in
Calculations
How many Cu atoms are in 0.50 mole of Cu?
Step 3 Use Avogadro’s number to write
conversion factors.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
64
Using Avogadro’s Number in
Calculations
How many Cu atoms are in 0.50 mole of Cu?
Step 4 Set up the problem to calculate the
number of particles.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
65
Learning Check
How many moles of CO2 are in 2.50 x 1024 molecules
of CO2?
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
66
Subscripts State Atoms and Moles
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
67
Moles of Elements in a Formula
The subscripts in a formula give
 the relationship of atoms in the formula and
 the moles of each element in 1 mole of a compound.
Glucose
C6H12O6
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
68
Conversion Factors from
Subscripts
Subscripts used for conversion factors relate moles of
each element in 1 mole of a compound
For aspirin, C9H8O4, can be written as:
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
69
Guide to Calculating Moles
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
70
Calculating Moles of an Element
How many moles of carbon are present in 2.3 moles
of C5H10O2, propyl acetate, the compound that
provides the odor and taste of pears.
Step 1 State the given and needed quantities.
Analyze the Problem.
© 2013 Pearson Education, Inc.
Given
Need
2.3 moles of C5H10O2
moles of C
Chapter 6, Section 3
71
Calculating Moles of an Element
How many moles of carbon are present in 2.3 moles
of C5H10O2, propyl acetate, the compound that
provides the odor and taste of pears.
Step 2 Write a plan to convert moles of
compound to moles of an element.
moles of C5H10O2
© 2013 Pearson Education, Inc.
subscript
Chapter 6, Section 3
moles of C
72
Calculating Moles of an Element
How many moles of carbon are present in 2.3 moles
of C5H10O2, propyl acetate, the compound that
provides the odor and taste of pears.
Step 3 Write equalities and conversion factors
using subscripts.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
73
Calculating Moles of an Element
How many moles of carbon are present in 2.3 moles
of C5H10O2, propyl acetate, the compound that
provides the odor and taste of pears.
Step 4 Set up the problem to calculate the moles
of an element.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
74
Learning Check
How many O atoms are in 0.150 mole of aspirin, C9H8O4?
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
75
General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 6
Chemical Reactions
and Quantities
6.5
Molar Mass
Lectures
© 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
76
Molar Mass
Molar mass is
 the mass of one mole
of a substance.
 the number of grams
that equals the atomic
mass of that element.
Molar mass is rounded to
the tenths (0.1 g) place
for use in this text.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
77
Learning Check
Give the molar mass of the following elements to
the nearest 0.1 g.
1. K
= ________
2. Sn = ________
3. Si
= ________
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
78
Guide to Calculating Molar Mass
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
79
Molar Mass of CaCl2
We calculate the molar mass of CaCl2 to the nearest
0.1 g as follows.
Analyze the Problem.
Given
Need
formula unit CaCl2 molar mass of Ca, Cl; CaCl2
Step 1 Obtain the molar mass of each element.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
80
Molar Mass of CaCl2
We calculate the molar mass of CaCl2 to the nearest
0.1 g as follows.
Step 2 Multiply each molar mass by the number of
moles (subscript) in the formula.
Grams from 1 mole of Ca
Grams from 2 moles of Cl
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
81
Molar Mass of CaCl2
We calculate the molar mass of CaCl2 to the nearest 0.1 g
as follows.
Step 3 Calculate the molar mass by adding the
masses of the elements.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
82
Learning Check
Determine the molar mass of K3PO4 to 0.1 g.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
83
Learning Check
Prozac, C17H18F3NO, is an antidepressant that inhibits
the uptake of serotonin by the brain. What is the molar
mass of Prozac?
A. 40.0 g/mole
B. 262 g/mole
C. 309 g/mole
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
84
One-Mole Quantities
32.1 g
© 2013 Pearson Education, Inc.
55.9 g
58.5 g
Chapter 6, Section 3
294.2 g
342.3 g
85
Conversion Factors from Molar
Mass
Methane (CH4), known as natural gas, is used in gas
stoves and gas heaters.
1 mole of CH4
=
16.0 g of CH4
The molar mass of methane can be written as
conversion factors
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
86
Calculations Using Molar Mass
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
87
Converting Mass to Moles, KCl
How many moles are present in a 65.1 g sample of KCl?
Step 1 State the given and needed quantities.
Analyze the Problem.
Given
Need
65.1 g of KCl
moles of KCl
Step 2 Write a plan to convert grams to moles.
grams of KCl
© 2013 Pearson Education, Inc.
Molar Mass
Chapter 6, Section 3
moles of KCl
88
Converting Mass to Moles, KCl
How many moles are present in a 65.1 g sample of KCl?
Step 3 Determine the molar mass and write
conversion factors.
1 mole of KCl = 74.6 g of KCl
Step 4 Set up the problem to convert grams to
moles.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
89
Learning Check
Acetic acid, C2H4O2, gives the sour taste to vinegar.
Calculate the moles of acetic acid present in a 25.8 g
sample.
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
90
Connections between Mass, Moles,
and Particles
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
91
Learning Check
Calcium carbonate, CaCO3 is found in antacid tablets.
If we have a 0.320 mole sample of CaCO3, how many
grams are present?
© 2013 Pearson Education, Inc.
Chapter 6, Section 3
92