Chapter 8
Chemical Equations and Chemical
Reactions
Table of Contents
Section 1 Describing Chemical Reactions (previous)
Section 2 Types of Chemical Reactions
Section 3 Activity Series of the Elements
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Objectives
• Define and give general equations for synthesis,
decomposition, single-displacement, and doubledisplacement reactions.
• Classify a reaction as a synthesis, decomposition,
single-displacement, double-displacement, or
combustion reaction.
• List three kinds of synthesis reactions and six kinds
of decomposition reactions.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Objectives, continued
• List four kinds of single-displacement reactions and
three kinds of double-displacement reactions.
• Predict the products of simple reactions given the
reactants.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
• There are several ways to classify chemical
reactions.
• The classification scheme described in this section
provides an introduction to five basic types of
reactions:
• synthesis
• decomposition
• single-displacement
• double-displacement
• combustion reactions
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Section 2 Types of Chemical
Reactions
Chapter 8
Synthesis Reactions
• In a synthesis reaction, also known as a
composition reaction, two or more substances
combine to form a new compound.
• This type of reaction is represented by the following
general equation.
A+X
AX
• A and X can be elements or compounds.
• AX is a compound
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions, continued
Reactions of Elements with Oxygen and Sulfur
• One simple type of synthesis reaction is the
combination of an element with oxygen to produce an
oxide of the element.
• Almost all metals react with oxygen to form oxides.
• example: 2Mg(s) + O2(g)
2MgO(s)
• Group 2 elements react in a similar manner, forming
oxides with the formula MO, where M represents
the metal.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions, continued
Reactions of Elements with Oxygen and Sulfur,
continued
• The Group 1 metals form oxides with the formula
M2O.
• example: Li2O
• The Group 1 and Group 2 elements react similarly
with sulfur, forming sulfides with the formulas M2S
and MS, respectively.
16Rb(s) + S8(s)
8Rb2S(s)
8Ba(s) + S8(s)
8BaS(s)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions, continued
Reactions of Elements with Oxygen and Sulfur,
continued
• Nonmetals also undergo synthesis reactions with
oxygen to form oxides.
• example: Sulfur reacts to form sulfur dioxide.
S8(s) + 8O2(g)
8SO2(g)
• example: Hydrogen reacts with oxygen to form
dihydrogen monoxide (water).
2H2(g) + O2(g)
2H2O(g)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions, continued
Reactions of Metals with Halogens
• Most metals react with the Group 17 elements, the
halogens, to form either ionic or covalent compounds.
• Group 1 metals react with halogens to form ionic
compounds with the formula MX, where M is the
metal and X is the halogen.
• example: 2Na(s) + Cl2(g)
2NaCl(s)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions, continued
Reactions of Metals with Halogens, continued
• Group 2 metals react with the halogens to form
ionic compounds with the formula MX2.
• example: Mg(s) + F2(g)
MgF2(s)
• Fluorine is so reactive that it combines with almost all
metals.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions, continued
Synthesis Reactions with Oxides
• Active metals are highly reactive metals.
• Oxides of active metals react with water to produce
metal hydroxides.
• example: Calcium oxide reacts with water to form
calcium hydroxide.
CaO(s) + H2O(l)
Ca(OH)2(s)
[CaO(s) + H-HO(l)  Ca(OH)2(s)]
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Synthesis Reactions with Oxides, continued
• Many oxides of nonmetals in the upper right portion of
the periodic table react with water to produce
oxyacids.
Example:
1. Sulfur dioxide + water yields sulfurous acid
SO2(g) + H2O(l)
H2SO3(aq)
2. Sulfurous Acid + water yields sulfuric acid (Acid Rain)
H2SO3(aq) + H2O(l)
H2SO4(aq)
• Certain metal oxides and nonmetal oxides react with
each other in synthesis reactions to form salts.
• example: CaO(s) + SO2(g)
CaSO3(s)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Decomposition Reactions
• In a decomposition reaction, a single compound
undergoes a reaction that produces two or more
simpler substances. s or compounds.
• Decomposition reactions are the opposite of
synthesis reactions.
• They are represented by the following general
equation.
AX
A+X
• AX is a compound.
• A and X can be elements or compounds.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Decomposition Reactions, continued
Decomposition of Binary Compounds
• The decomposition of a substance by an electric
current is called electrolysis. (electricity lyses)
• example: 2H O(l) ¾electricity
¾¾¾
® 2H2 (g) + O2 (g)
2
• Oxides of the less-active metals, which are located in
the lower center of the periodic table, decompose into
their elements when heated.
• example: 2HgO(s) ¾D¾
® 2Hg(l) + O2 (g)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Decomposition Reactions, continued
Decomposition of Metal Carbonates
D
CaCO3 (s) ¾¾
® CaO(s) + CO2 (g)
Decomposition of Metal Hydroxides
D
Ca(OH)2 (s) ¾¾
® CaO(s) + H2O(g)
Decomposition of Metal Chlorates
D
2KClO3 (s) ¾MnO
¾¾¾
® 2KCl(s) + 3O2 (g)
(s)
2
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Decomposition Reactions, cont.
Decomposition of Acids
1. Arrhenius Acid – gives H+ in aqueous solution
2. Bronsted-Lowry Acid – proton donor
• Certain acids decompose into nonmetal oxides
and water.
example: Carbonic acid is unstable and
decomposes readily at room temperature to
produce carbon dioxide and water.
H2CO3 (aq) ® CO2 (g) + H2O(l)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions
• In a single-displacement reaction, also known as a
replacement reaction, one element replaces a similar
element in a compound.
• Many single-displacement reactions take place in
aqueous solution.
• Single-displacement reactions can be represented by
the following general equations.
A + BX
AX + B or Y + BX
BY + X
• A, B, X, and Y are elements. AX, BX, and BY are compounds.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions
Displacement of a Metal in a Compound by Another
Metal
• Aluminum is more active than lead.
2Al(s) + 3Pb(NO3)2(aq)
3Pb(s) + 2Al(NO3)3(aq)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions, continued
Displacement of Hydrogen in Water by a Metal
• The most-active metals, such as those in Group 1,
react vigorously with water to produce metal hydroxides
and hydrogen.
2Na(s) + 2H2O(l)
2NaOH(aq) + H2(g)
• Less-active metals, such as iron, react with steam to
form a metal oxide and hydrogen gas.
3Fe(s) + 4H2O(g)
Fe3O4(s) + 4H2(g)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions, continued
Displacement of Hydrogen in an Acid by a Metal
• The more-active metals react with certain acidic
solutions, such as hydrochloric acid and dilute sulfuric
acid, replacing the hydrogen in the acid.
• The reaction products are a metal compound (a salt)
and hydrogen gas.
Mg(s) + 2HCl(aq)
H2(g) + MgCl2(aq)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Single-Displacement Reactions, continued
Displacement of Halogens
• Fluorine is the most-active halogen.
• It can replace any of the other halogens in their
compounds.
• In Group 17 each element can replace any element
below it, but not any element above it.
Cl2(g) + 2KBr(aq)
2KCl(aq) + Br2(l)
F2(g) + 2NaCl(aq)
2NaF(aq) + Cl2(g)
Br2(l) + KCl(aq)
no reaction
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Double-Displacement Reactions
• In double-displacement reactions, the ions of two
compounds exchange places in an aqueous solution to
form two new compounds.
• One of the compounds formed is usually a precipitate,
an insoluble gas that bubbles out of the solution, or a
molecular compound, usually water.
• The other compound is often soluble and remains
dissolved in solution.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Double-Displacement Reactions, continued
• A double-displacement reaction is represented by the
following general equation.
AX + BY
AY + BX
• A, X, B, and Y in the reactants represent ions.
• AY and BX represent ionic or molecular
compounds.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Double-Displacement Reactions, continued
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Double-Displacement Reactions, continued
Formation of a Precipitate
• The formation of a precipitate occurs when the
cations of one reactant combine with the anions of
another reactant to form an insoluble or slightly
soluble compound.
• example:
2KI(aq) + Pb(NO3)2(aq)
PbI2(s) + 2KNO3(aq)
• The precipitate forms as a result of the very strong attractive
forces between the Pb2+ cations and the I anions.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Double-Displacement Reactions, continued
Formation of a Gas
FeS(s) + 2HCl(aq)
H2S(g) + FeCl2(aq)
Formation of Water
HCl(aq) + NaOH(aq)
NaCl(aq) + H2O(l)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Combustion Reactions
• In a combustion reaction, a substance combines with
oxygen, releasing a large amount of energy in the form
of light and heat.
• example: combustion of hydrogen
2H2(g) + O2(g)
2H2O(g)
• example: combustion of propane
C3H8(g) + 5O2(g)
3CO2(g) + 4H2O(g)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Determining Reaction Types
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Identifying Reactions and Predicting
Products
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Identifying Reactions and Predicting
Products
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 2 Types of Chemical
Reactions
Identifying
Reactions and
Predicting
Products
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 3 Activity Series of the
Elements
Objectives
• Explain the significance of an activity series.
• Use an activity series to predict whether a given
reaction will occur and what the products will be.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 3 Activity Series of the
Elements
• The ability of an element to react is referred to as the
element’s activity.
• The more readily an element reacts with other substances,
the greater its activity is.
• An activity series is a list of elements organized
according to the ease with which the elements
undergo certain chemical reactions.
• For metals, greater activity means a greater ease of loss of
electrons, to form positive ions.
• For nonmetals, greater activity means a greater ease of
gain of electrons, to form negative ions.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 3 Activity Series of the
Elements
• The order in which the elements are listed is usually
determined by single-displacement reactions.
• The most-active element is placed at the top in the
series.
• It can replace each of the elements below it from
a compound in a single-displacement reaction.
• Activity series are used to help predict whether
certain chemical reactions will occur.
• Activity series are based on experiment.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Section 3 Activity Series of the
Elements
Activity Series of the
Elements
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
End of Chapter 8 Show
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
1. According to the law of conservation of mass, the total
mass of the reacting substances is
A. always more than the total mass of the products.
B. always less than the total mass of the products.
C. sometimes more and sometimes less than the total
mass of the products.
D. always equal to the total mass of the products.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
2. To balance a chemical equation, you may adjust the
A. coefficients.
B. subscripts.
C. formulas of the products.
D. either the coefficients or the subscripts.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
3. Which is the correct chemical equation for the
following formula equation:
(NH4)2S
NH3 + H2S?
A. 2(NH4)2S
2NH3 + H2S2
B. 2(NH4)2S
2NH3 + H2S
C. (NH4)2S
2NH3 + H2S
D. None of the above
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
4. Select the missing reactant(s) for the doubledisplacement reaction that produces PF5 and AsCl3.
A. PCl5 and AsF3
B. PCl3 and AsF5
C. PCl3 and AsF3
D. None of the above
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
5. Select the missing reactant for the following
combustion reaction: 2______ + 15O2
14CO2 + 6H2O.
A. C14H12
B. C14H12O4
C. C7H6
D. C7H6O2
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
6. A mixture consists of Ag, Pb, and Fe metals. Which of
these metals will react with ZnCl2?
A. Ag(s)
B. Pb(s)
C. Fe(s)
D. None of these metals
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Multiple Choice
7. Which of the following statements is true about the
reaction 2F2 + 2H2O
4HF + O2?
A. Two grams of O2 are produced when 2 g F2 reacts
with 2 g H2O.
B. Two moles of HF are produced when 1 mol F2
reacts with 1 mol H2O.
C. For every 2 mol O2 produced, 6 mol HF are
produced.
D. For every 1 mol H2O that reacts, 2 mol O2 are
produced.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Short Answer
8. Determine the products and write a balanced equation
for the reaction of solid magnesium and water.
Answer:
Mg(s) + 2H2O(l)
Mg(OH)2(aq) + H2(g)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Short Answer
9. A precipitation of iron(III) hydroxide is produced by
reacting an aqueous solution of iron(III) chloride with
an aqueous solution of sodium hydroxide. Write a
balanced chemical equation.
Answer:
FeCl3(aq) + 3NaOH(aq)
Fe(OH)3(s) + 3NaCl(s)
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Extended Response
10. List the hypothetical metals A, E, M, and R in
increasing order of reactivity by using the reaction
data in the table below. The reaction of interest is of
the form C + ZX
CX + Z. Explain your reasoning.
AX
EX
MX
RX
A
_____
no reaction
reaction
no reaction
E
reaction
_____
reaction
reaction
M
no reaction
no reaction
_____
no reaction
R
reaction
no reaction
reaction
_____
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Extended Response
10. List the hypothetical metals A, E, M, and R in
increasing order of reactivity by using the reaction
data in the table below. The reaction of interest is of
the form C + ZX
CX + Z. Explain your reasoning.
Answer: The metals in increasing order of reactivity are M, A, R, and
E. M is the least reactive because it shows no reaction in a
single-displacement reaction with any of the other metals. A is the
next least reactive because it will react in a single-displacement
reaction with only M. E is the most reactive metal of the series
because E will react in a single-displacement reaction with the
other three metals.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 8
Standardized Test Preparation
Extended Response
11. Calcium hypochlorite, Ca(OCl)2, is a bleaching agent
produced from sodium hydroxide, calcium hydroxide,
and chlorine. Sodium chloride and water are also
produced in the reaction. Write the balanced chemical
equation. If 2 mol NaOH react, how many moles of
calcium hypochlorite can be produced?
Answer: The balanced chemical equation is
2NaOH + Ca(OH)2 + 2Cl2
Ca(OCl)2 + 2NaCl + H2O.
If 2 mol NaOH react, then 1 mol Ca(OCl)2 can be
produced.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.