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Chapter 7 Chemical Reactions

7.4

Types of Reactions

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Type of Reactions

Chemical reactions can be classified as • Combination reactions.

• Decomposition reactions.

• Single Replacement reactions.

• Double Replacement reactions.

• Combustion reactions.

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Combination

In a combination reaction,• Two or more elements form one product.• Or simple compounds combine to form one

product.

+

2Mg(s) + O2(g) 2MgO(s)

2Na(s) + Cl2(g) 2NaCl(s)

SO3(g) + H2O(l) H2SO4(aq)

A B A B

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Formation of MgO (see demo)

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Decomposition (Elephant toothpaste demo)

In a decomposition reaction, • One substance splits into two or more

simpler substances.

2HgO(s) 2Hg(l) + O2(g)

2KClO3(s) 2KCl(s) +

3O2(g)

1 H2O2(aq) KI (aq) 1 H2 (g) + 1

O2(g)

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Decomposition of HgO

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Learning Check

Classify the following reactions as

1) combination or 2) decomposition:

___A. H2(g) + Br2(g) 2HBr(l)

___B. Al2(CO3)3(s) Al2O3(s) + 3CO2(g)

___C. 4Al(s) + 3C(s) Al4C3(s)

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Solution

Classify the following reactions as

1) combination or 2) decomposition:

1 A. H2(g) + Br2(g) 2HBr(l)

2 B. Al2(CO3)3(s) Al2O3(s) + 3CO2(g)

1 C. 4Al(s) + 3C(s) Al4C3(s)

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Single Replacement (demo)

In a single replacement reaction, • One element takes the place of a different

element in a reacting compound.

Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s)

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Zn and HCl is a Single Replacement Reaction

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Double Replacement (demo lead nitrate and KI)

In a double replacement reaction,• Two elements in the reactants exchange places.

AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

ZnS(s) + 2HCl(aq) ZnCl2(aq) + H2S(g)

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Example of a Double Replacement

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Learning Check

Classify the following reactions as

1) single replacement 2) double replacement

__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) 2Fe(s) + 3CO(g)

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Solution

Classify the following reactions as

1) single replacement 2) double replacement

1 A. 2Al(s) + 3H2SO4(aq) Al2(SO4)3(s) + 3H2(g)

2 B. Na2SO4(aq) + 2AgNO3(aq) Ag2SO4(s) + 2NaNO3(aq)

1 C. 3C(s) + Fe2O3(s) 2Fe(s) + 3CO(g)

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In a combustion reaction,

• A compound such as carbon reacts with oxygen, O2.

C(s) + O2(g) CO2(g)

CH4(g) + 2O2(g) CO2 (g) + 2H2O(g)

C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)

• Fuels burned in oxygen produce CO2, H2O, and energy.

Combustion (demo bunsen burner)

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Example of a Combustion Reaction

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Learning Check

Balance the combustion equation

___C5H12 + ___O2 ___CO2 +

___H2O

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Solution

Balance the combustion equation

1 C5H12 + 8 O2 5 CO2 + 6 H2O

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Summary of Reaction Types

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Table 7.4

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Learning Check

Identify each reaction as: 1) combination 2) decomposition 3) combustion4) single replacement 5) double replacement

A. 3Ba(s) + N2(g) Ba3N2(s)B. 2Ag(s) + H2S(aq) Ag2S(s) + H2(g)C. SiO2(s) + 4HF(aq) SiF4(s) + 2H2O(l)D. PbCl2(aq) + K2SO4(aq) 2KCl(aq) + PbSO4(s)E. K2CO3(s) K2O(aq) + CO2(g)F. C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g)

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Solution

Identify each reaction as: 1) combination 2) decomposition 3) combustion4) single replacement 5) double replacement

1 A. 3Ba(s) + N2(g) Ba3N2(s)

4 B. 2Ag(s) + H2S(aq) Ag2S(s) + H2(g)

5 C. SiO2(s) + 4HF(aq) SiF4(s) + 2H2O(l)

5 D. PbCl2(aq) + K2SO4(aq) 2KCl(aq) + PbSO4(s)

2 E. K2CO3(s) K2O(aq) + CO2(g)

3 F. C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g)