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Chapter 5 Chemical Reactions and Quantities

5.3Types of Reactions

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Type of Reactions

Chemical reactions can be classified as

• combination reactions.• decomposition reactions.• single replacement reactions.• double replacement 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

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Decomposition

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

substances.

2HgO(s) 2Hg(l) + O2(g)2KClO3(s) 2KCl(s) + 3 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

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

In a double replacement, • 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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Learning Check

Identify each reaction as 1) combination 2) decomposition 3) single replacement 4) 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)

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Solution

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

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

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

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

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