Types of
Chemical
Reactions
Review
A chemical equation describes a chemical
change.
The Law of Conservation of Mass says that
the number and kind of atoms going INTO
a chemical reaction must be the same as
the number and kind of atoms coming OUT.
Balancing an equation makes it obey the
Law of Conservation of Mass.
Types of Reactions
The six types of chemical reactions we
will discuss are:
Synthesis
Decomposition
Single Displacement
Double Displacement
Acid-Base
Combustion
Synthesis Reactions
Two or more substances
combine to form one
substance.
The general form is
A + X  AX
Example:
2Mg + O2  2MgO
Decomposition Reactions
One molecule breaks
down to form two or
more substances.
The general form is
AX  A + X
Example:
2H2O  2H2 + O2
Single Displacement Reactions
A single element switches places
with another element in a chemical
compound.
The general form is A + BX  AX + B
Example:
Ni + 2AgNO3  2Ag + Ni(NO3)2
Single Displacement Reactions
Example:
Ni + 2AgNO3  2Ag + Ni(NO3)2
Ni + 2AgNO3 
Nickel replaces the metallic
ion Ag+.
The silver becomes free
silver and the nickel
becomes the nickel(II) ion.
Double Displacement Reactions
The cations of two
compounds exchange
places with each other.
The general form is:
AX + BY  AY + BX
Double Displacement
Example:
NaOH + CuSO4 
The Na+ and Cu2+ switch places.
Na+ combines with SO42- to form Na2SO4.
Cu2+ combines with OH- to form Cu(OH)2
2NaOH + CuSO4  Na2SO4 + Cu(OH)2
Acid-Base
Acid-base reactions are double displacement
reactions which takes place when an acid and
base react with each other.
HA + BOH → H2O + BA
Acid
Example:
Base
HBr + NaOH → NaBr + H2O
The H+ ion in the acid reacts with the OH- ion in the
base, causing the formation of an ionic salt (NaBr)
and water.
Combustion Reaction
When a compound containing carbon and
hydrogen combines with oxygen, the
products formed are heat, water, and
carbon dioxide.
CH4 + 2O2  CO2 + 2H2O
1) Does the reaction look like this:
CxHx + O2  CO2 + H2O ?
If yes - combustion reaction. If no...
2) Is there only one product?
If yes - synthesis reaction. If no...
3) Is there only one reactant?
If yes - decomposition reaction. If no...
4) Are any reactants only one kind of element?
If yes - single displacement reaction. If no...
5) Is water a product of this reaction?
If yes - acid base reaction.
If not - double displacement reaction.
Learning Check...
Classify each of the following reactions:
H2 + Cl2  2HCl
Synthesis
Ca + 2H2O  Ca(OH)2 + H2
Single displacement
Learning Check...
Classify each of the following reactions:
2CO + O2  2CO2
Synthesis
2KClO3  2KCl + 3O2
Decomposition
Learning Check...
Classify each of the following reactions:
CH3SH + 3O2  CO2 + 2H2O + SO2
Combustion
Zn + 2HCl  ZnCl2 + H2
Single displacement
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