Section 9.2 Classifying Chemical Reactions
• Classify chemical
reactions.
• Identify the
characteristics of
different classes of
chemical reactions.
metal: an element that is
a solid at room
temperature, a good
conductor of heat and
electricity, and is generally
shiny
Section 9.2 Classifying Chemical Reactions
(cont.)
synthesis reaction
combustion reaction
decomposition reaction
double-replacement
reaction
precipitate
single-replacement
reaction
There are four types of chemical
reactions: synthesis, combustion,
decomposition, and replacement
reactions.
Types of Chemical Reactions
• Chemists classify reactions in order to
organize the many types.
• A synthesis reaction is a reaction in which
two or more substances react to produce a
single product.
Types of Chemical Reactions (cont.)
• When two elements react, the reaction is
always a synthesis reaction.
Types of Chemical Reactions (cont.)
• In a combustion reaction, oxygen
combines with a substance and releases
energy in the form of heat and light.
• Heated hydrogen reacts with oxygen to
produce heat and water in a combustion
reaction. This is also a synthesis reaction.
Decomposition Reactions
• A decomposition reaction is one in which
a single compound breaks down into two or
more elements or new compounds.
• Decomposition reactions often require an
energy source, such as heat, light, or
electricity, to occur.
Replacement Reactions
• A reaction in which the atoms of one
element replace the atoms of another
element in a compound is called a single
replacement reaction.
A + BX → AX + B
Replacement Reactions (cont.)
• A metal will not always
replace a metal in a
compound dissolved in
water because of differing
reactivities.
• An activity series can be
used to predict if reactions
will occur.
Replacement Reactions (cont.)
• Halogens frequently replace other
halogens in replacement reactions.
• Halogens also have different reactivities and
do not always replace each other.
Replacement Reactions (cont.)
• Double replacement reactions occur
when ions exchange between two
compounds.
• This figure shows a generic double
replacement equation.
Replacement Reactions (cont.)
• The solid product produced during a
chemical reaction in a solution is called a
precipitate.
• All double replacement reactions produce
either water, a precipitate, or a gas.
Replacement Reactions (cont.)
• This table shows the steps to write double
replacement reactions.
Replacement Reactions (cont.)
• This table summarizes different ways to
predict the products of a chemical reaction.
Section 9.2 Assessment
Which of the following is NOT one of the
four types of reactions?
A. deconstructive
B. synthesis
D
A
0%
C
D. double replacement
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. single replacement
Section 9.2 Assessment
The following equation is what type of
reaction?
KCN(aq) + HBr(aq) → KBr(aq) + HCN(g)
A. deconstructive
A
0%
D
D. double replacement
C
C. single replacement
A. A
B. B
C. C
0%
0%
0%
D. D
B
B. synthesis