Classifying chemical reactions
Why?
• When we classify, we are able to organize
information and understand the material
better.
Quick review: Symbolizing chemical reactions
coefficients
reactants
products
5 Classes of Chemical Reactions
1.
2.
3.
4.
5.
Synthesis:
To make
Decomposition:
To break down
Single replacement: Single Substitute
Double replacement: Two substitutes
Combustion: To burn
1. Synthesis Reactions
How do we recognize a synthesis reaction?
a. A single product forms from two or more
reactants.
Example:
2 MgO
2 Mg + __ O2  __
__
General format:
A + B  AB
How does this cartoon symbolize a
synthesis reaction?
A
B
AB
Indicate which letter each animal represents.
Synthesis reaction demonstration
2. Decomposition Reaction
How do we recognize a decomposition reaction?
a. A reactant breaks down into two or more
products
Example:
H2O2 H2O + O2
General Format:
AB  A + B
How does this cartoon symbolize a
decomposition reaction?
AB
A
B
Indicate which letter each figure represents.
Decomposition example
2 Na + __Cl
2
__NaCl
 __
2
3. Single Replacement Reactions
How do we recognize a single replacement reaction?
a. A single element reacts with a compound
b. Products are a different single element and a different
compound
Example:
2 HCl ---> __ ZnCl2 + __ H2
__ Zn + __
General format:
A + BC  AC +B
How does this cartoon symbolize a single
replacement reaction?
A
BC
AC
B
Indicate which letter each figure represents.
Single replacement reaction example
4. Double Replacement Reaction
How do we recognize a double replacement reaction?
a. Two compounds exchange partners and form two new
compounds
b. This reaction often produces a precipitate
Example:
2 HCl ---> __ FeCl2 + __ H2S
__ FeS + __
General format:
AB + CD  AD + CB
How does this cartoon symbolize a double
replacement reaction?
A
B
C
D
C
B
A
D
Indicate which letter each figure represents.
Example of
a double
replacement
reaction
5. Combustion
Reactions
How do we recognize a combustion reaction?
a. A compound containing CHO reacts with
oxygen
b. Products are carbon dioxide and water
Example (combustion of ethanol):
1 CH3CH2OH + __
3 O2  __
2 CO2 +__
3 H2 O
__
General format:
•CHO + O2  CO2 + H2O
Example of a
combustion reaction