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Chapter 8 Lecture
Basic Chemistry
Type of Reactions
Fifth Edition
Chapter 8
Chemical Reactions
8.3 Types of Reactions
The types of chemical reactions can be
classified as
• combination reactions
• decomposition reactions
Learning Goal Identify a
chemical reaction as a
combination, decomposition,
single replacement, double
replacement, or combustion.
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• single-replacement reactions
• double-replacement reactions
In a combination reaction, two
or more substances combine to
form one substance as the
product.
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Combination
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Formation of MgO
In a combination reaction,
• two or more elements form one product
• or simple compounds combine to form one
product
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2Mg(s) + O2(g)
2Na(s) + Cl2(g)
2MgO(s)
2NaCl(s)
SO3(g) + H2O(l)
H2SO4(aq)
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Decomposition
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Decomposition of HgO
In a decomposition reaction,
• one reactant splits into two or more simpler
substances.
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2HgO(s)
2Hg(l) + O2(g)
2KClO3(s)
2KCl(s) + 3O2(g)
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Learning Check
Single Replacement
Classify the following reactions as
(C) combination or (D) decomposition:
___1. H2(g) + Br2(g)
In a single-replacement reaction,
• one element takes the place of a different
element in a reacting compound.
2HBr(l)
___2. Al2(CO3)3(s)
Al2O3(s) + 3CO2(g)
___3. 4Al(s) + 3C(s)
Al4C3(s)
Zn(s) + 2HCl(aq)
ZnCl2(aq) + H2(g)
Fe(s) + CuSO4(aq)
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Zn and HCl in a SingleReplacement Reaction
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FeSO4(aq) + Cu(s)
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Double-Replacement
In a double-replacement reaction,
• two elements in the reactants exchange places.
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Example of a DoubleReplacement
AgNO3(aq) + NaCl(aq)
AgCl(s) + NaNO3(aq)
ZnS(s)
ZnCl2(aq) + H2S(g)
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+ 2HCl(aq)
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Learning Check
Classify the following reactions as
(SR) single replacement or (DR) double replacement.
__1. 2Al(s) + 3H2SO4(aq)
Al2(SO4)3(s) + 3H2(g)
__2. Na2SO4(aq) + 2AgNO3(aq)
__3. 3C(s) + Fe2O3(s)
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Ag2SO4(s) + 2NaNO3(aq)
2Fe(s) + 3CO(g)
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Summary of Reaction Types
Learning Check
Identify each type of reaction as
(C) combination
(D) decomposition
(SR) single replacement
(DR) double replacement
__1. 3Ba(s) + N2(g)
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Ba3N2(s)
__2. 2Ag(s) + H2S(aq)
Ag2S(s) + H2(g)
__3. SiO2(s) + 4HF(aq)
SiF4(s) + 2H2O(l)
__4. PbCl2(aq) + K2SO4(aq)
2KCl(aq) + PbSO4(s)
__5. K2CO3(s)
K2O(aq) + CO2(g)
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Combustion
Combustion of Propane
In a combustion reaction,
In a combustion reaction,
• an organic compound reacts with oxygen, O2
• propane reacts with oxygen, O2,
• the products are CO2, H2O, and energy
C3H8(g) + 5O2(g)
• for methane, the balanced equation is
CH4(g) + 2O2(g)
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
CO2 (g) + 2H2O(g) + heat
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Learning Check

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Combustion of Alcohols
Balance the combustion equation for pentane.
__C5H12 + __O2

3CO2(g) + 4H2O(g) + heat
An alcohol such as ethanol undergoes combustion.
__ CO2 + __H2O + heat
CH3─CH2─OH + 3O2

2CO2 + 3H2O + heat
A dessert is heated by a combustion reaction.
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The Algebraic Way
Some reactions are difficult to balance by
inspection and can be balanced using some
simple algebra.
Example:
+
+
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+
+
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