Dr Seemal Jelani Chem-100

Chemical Reactions and

Quantities

Types of Reactions

Oxidation-Reduction Reactions

04/20/23 1

Dr Seemal Jelani Chem-100

Type of Reactions

Chemical reactions are classified into four general types

Combination

Decomposition

Single Replacement

Double Replacement

04/20/23 2

Dr Seemal Jelani Chem-100

Combination (Synthesis)

Two or more elements or simple compounds combine to form (synthesize) one product

A + B AB

2Mg + O2 2MgO

2Na + Cl2 2NaCl

SO3 + H2O H2SO4

04/20/23 3

Dr Seemal Jelani Chem-100

Decomposition

One substance is broken down (split) into two or more simpler substances.

AB A + B

2HgO 2Hg + O2

2KClO3 2KCl + 3 O2

04/20/23 4

Dr Seemal Jelani Chem-100

Learning Check R1

Classify the following reactions as

1) combination or 2) decomposition:

___A. H2 + Br2 2HBr

___B. Al2(CO3)3 Al2O3 + 3CO2

___C. 4 Al + 3C Al4C3

04/20/23 5

Dr Seemal Jelani Chem-100

Solution R1

Classify the following reactions as

1) combination or 2) decomposition:

_1_A. H2 + Br2 2HBr

_2_B. Al2(CO3)3 Al2O3 + 3CO2

_1_C. 4 Al + 3C Al4C3

04/20/23 6

Dr Seemal Jelani Chem-100

Single Replacement

One element takes the place of an element in a reacting compound.

A + BC AB + C

Zn + 2HCl ZnCl2 + H2

Fe + CuSO4 FeSO4 + Cu

04/20/23 7

Dr Seemal Jelani Chem-100

Double Replacement

Two elements in reactants take the place of each other

AB + CD AD + CB

AgNO3 + NaCl AgCl + NaNO3

ZnS + 2HCl ZnCl2 + H2S

04/20/23 8

Dr Seemal Jelani Chem-100

Learning Check R2

Classify the following reactions as

1) single replacement

2) double replacement

__A. 2Al + 3H2SO4 Al2(SO4)3 + 3H2

__B. Na2SO4 + 2AgNO3 Ag2SO4 + 2NaNO3

__C. 3C + Fe2O3 2Fe + 3CO04/20/23 9

Dr Seemal Jelani Chem-100

Solution R2

Classify the following reactions as

1) single replacement

2) double replacement

1_A. 2Al + 3H2SO4 Al2(SO4)3 + 3H2

2_B. Na2SO4 + 2AgNO3 Ag2SO4 + 2NaNO3

1_C. 3C + Fe2O3 2Fe + 3CO04/20/23 10

Dr Seemal Jelani Chem-100

Combustion

A reaction in which a compound (often

carbon) reacts with oxygen

C + O2 CO2

CH4 + 2O2 CO2 + 2H2O

C3H8 + 5O2 3CO2 + 4H2O

C6H12O6 + 6O2 6CO2 + 6H2O

04/20/23 11

Dr Seemal Jelani Chem-100

Learning Check R3

Balance the combustion equation

___C5H12 + ___O2 ___CO2 + ___H2O

04/20/23 12

Dr Seemal Jelani Chem-100

Solution R3

Balance the combustion equation

1 C5H12 + 8 O2 5 CO2 + 6 H2O

04/20/23 13

Dr Seemal Jelani Chem-100

Oxidation and Reduction

Reactions that involve a loss or gain of electrons

Occurs in many of the 4 types of reactions and combustion

Important in food metabolism, batteries, rusting of metals

04/20/23 14

Dr Seemal Jelani Chem-100

Requirements for Oxidization-Reduction

Electrons are transferred

Two processes occur

Oxidation = Loss of electrons (LEO)

Zn Zn2+ + 2e-

Reduction = Gain of electrons (GER)

Cu2+ + 2e- Cu

04/20/23 15

Dr Seemal Jelani Chem-100

Balanced Red-Ox Equations

Combine the oxidation and reduction reactions to make

Loss of electrons = Gain of electrons

Zn + Cu2+ + 2e- Zn2+ + 2e- + Cu

Zn + Cu2+ Zn2+ + Cu

04/20/23 16

Dr Seemal Jelani Chem-100

Gain/Loss of Hydrogen

In organic and biological reactions

oxidation = Loss of H

reduction = Gain of H

04/20/23 17

Dr Seemal Jelani Chem-100

Learning Check R3

Identify the following as an 1) oxidation or a reduction process:

__A. Sn Sn4+ + 4e-

__B. Fe3+ + 1e- Fe2+

__C. Cl2 + 2e- 2Cl-

04/20/23 18

Dr Seemal Jelani Chem-100

Solution R3

Identify the following as an 1) oxidation or a reduction process:

1_ A. Sn Sn4+ + 4e-

2_ B. Fe3+ + 1e- Fe2+

2_ C. Cl2 + 2e- 2Cl-

04/20/23 19

Dr Seemal Jelani Chem-100

Learning Check R4

In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction

Ag+ + Cl- Ag + Cl

A. Which reactant is oxidized

1) Ag+ 2) Cl- 3) Ag

B. Which reactant is reduced?

1) Ag+ 2) Cl- 3) Cl

04/20/23 20

Dr Seemal Jelani Chem-100

Solution R4

In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction

Ag+ + Cl- Ag + Cl

A. Which reactant is oxidized

2) Cl- Cl- Cl + e-

B. Which reactant is reduced?

1) Ag+ Ag+ + e- Ag

04/20/23 21

Dr Seemal Jelani Chem-100

04/20/23 22