Chapter 24 Lesson 3
Classifying Chemical Reactions
Types of Reactions

Chemists have defined five main
categories
combustion
 synthesis
 decomposition
 single displacement
 double displacement

Combustion Reactions

Combustion reaction.
occurs when a substance reacts
with oxygen to produce energy
in the form of heat and light.
 also produce one or more
products that contain the
elements in the reactants

Combustion


The burning of a substance in O2 to
produce heat
Hydrocarbons (CxHy) always form CO2
and H2O
CxHy+O2  CO2+H2O
CH4 + 2O2  CO2 + 2H2O
Synthesis


the combination of 2 or more
substances to form a compound
only one product forms
A + B  AB
2P + 3Br2  2PBr3
Decomposition Reactions

A decomposition reaction
reverse of a synthesis
 decomposition reaction occurs when one
substance breaks down, or decomposes, into
two or more substances
 most require the use of heat, light, or
electricity.

Decomposition


a compound breaks down into 2 or
more simpler substances
only one reactant
AB  A + B
2H2O2  2H2O + O2
Single Replacement

one element replaces another in a
compound
metal replaces metal (+)
 nonmetal replaces nonmetal (-)

A + BC  AC + B
Zn + 2HCl  ZnCl2 + H2
The Activity Series

Predict
which metal will replace another using the
diagram
 lists metals according to how reactive they
are


A metal

replace any less active metal.
Double Replacement


ions in two compounds “change
partners”
cation(+) of one compound combines
with anion(-) of the other
AB + CD  AD + CB
2KOH + CuSO4  K2SO4 + Cu(OH)2
Double Displacement

Double displacement reaction


takes place if a precipitate, water, or a gas
forms when two ionic compounds in solution
are combined.
Precipitate

insoluble compound that comes out of solution
during this type of reaction.
Oxidation-Reduction
Reactions

Gain or loss of electrons


characteristic that is common to many
chemical reactions
Oxidation

describes the loss of electrons and the term
reduction to describe the gain of electrons.
Oxidation-Reduction
Reactions
Chemical reactions
involving electron
transfer
often involve oxygen,
which is very reactive,
pulling electrons from
metallic elements.
Corrosion of metal is
a visible result.
Oxidation-Reduction
Reactions

Reduced


gains an electron or electrons obviously
becomes more negative
Oxidized

the substance that loses an electron or
electrons then becomes more positive
Oxidation-Reduction
Reactions

Reduction


electrons that were pulled from one atom
were gained by another atom in a chemical
reaction
Redox

Reduction is the partner to oxidation; the two
always work as a pair