General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 1

Chapter 6 Chemical Reactions and Quantities

6.2Types of Reactions

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 2

Types of Reactions

Chemical reactions can be classified as combination reactions decomposition reactions single replacement reactions double replacement reactions

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 3

Combination Reaction

In a combination reaction, two or more elements (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)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 4

Formation of MgO

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 5

Decomposition Reaction

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)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 6

Decomposition of HgO

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 7

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)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 8

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)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 9

Single Replacement Reaction

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)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 10

Zn and HCl Combine in a Single Replacement Reaction

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 11

Double Replacement Reaction

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)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 12

Example of Double Replacement

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 13

Learning Check

Classify each of the following reactions as:

1) single replacement or 2) double replacement

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

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

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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 14

Solution

Classify each of the following reactions as:

1) single replacement or 2) double replacement

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

2 B. Na2SO4(aq) + 2AgNO3(aq)

Ag2SO4(s) + 2NaNO3(aq)

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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 15

Learning Check

Identify each of the following reactions as:

1) combination 2) decomposition

3) single replacement 4) double replacement

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

B. Hg(l) + 2HCl(aq) HgCl2(aq) + H2(g)

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

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

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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 16

Solution

Identify each of the following reactions as:

1) combination 2) decomposition

3) single replacement 4) double replacement

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

3 B. Hg(l) + 2HCl(aq) HgCl2(s) + H2(g)

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

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

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