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Complete #3 on Page 29
Name the reaction type for each of the
following:
Redox Reactions
Synthesis
(Combination)
Single
Replacement
Decomposition
Double
Replacement
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Synthesis
A +
Decomposition
B
AB
AB
A + B
Single
AB + C
Replacement
A +CB
Double A B + C D
Replacement
AD + C B
Decomposition and Redox:
At the conclusion of our time together,
you should be able to:
1. Identify decomposition chemical reactions
2. Show the change in oxidation numbers for
this type of reaction
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2. Decomposition Reactions
•
•
•
•
•
Decomposition reactions occur when a
compound breaks up into the elements or in a
few to simpler compounds
1 Reactant  Product + Product
In general: AB  A + B
Example: 2 H2O  2H2 + O2
Example: 2 HgO  2Hg + O2
2. Decomposition Reactions
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•
•
•
•
•
For Decomposition reactions to occur we
need energy in the form of:
Heat
Light
Electricity
Mechanical Shock
Or a Catalyst
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Decomposition Reactions
•
Another view of a decomposition reaction:
Decomposition Exceptions
•
Carbonates and chlorates are special case
decomposition reactions that do not go to the
elements. You should be able to recognize
these as decomposition only.
• Carbonates (CO32-) decompose to carbon
dioxide and a metal oxide
• Example: CaCO3  CO2 + CaO
• Chlorates (ClO3-) decompose to oxygen gas
and a metal chloride
• Example: 2 Al(ClO3)3  2 AlCl3 + 9 O2
• There are other special cases, but we will not
explore those in this class
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Practice
•
•
•
Predict the products. Then, write and balance
the following decomposition reaction equations:
Solid Lead (IV) oxide decomposes
PbO2(s)  Pb + O2
Aluminum nitride decomposes
AlN(s)  Al + N2
Practice of Decomposition and Redox
Predict the products, balance the following
reactions and show the change in oxidation
numbers :
H2 O

H2 + O 2
•
2 H2O

2 H2 + O2
Each H gains 1e- reduction, oxidizing agent
Each O loses 2e- oxidation, reducing agent
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Decomposition and Redox:
Let’s see if you can:
1. Identify decomposition chemical reactions
2. Show the change in oxidation numbers for
this type of reaction
Practice
Identify the type of reaction for each of the
following decomposition reactions, and write the
balanced equation:
BaCO3(s) 
BaO + CO2
NI3(s)  N2 + I2
2, 1, 3
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Practice of Decomposition and Redox
Predict the products, balance the following
reactions and show the change in oxidation
numbers:
FeO

Fe + O2
•
2 FeO

Each Fe(II) gains 2eEach O loses 2e-
2 Fe + O2
reduction, oxidizing agent
oxidation, reducing agent
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