Decomposition and RedoxDecomposition and Redox

Decomposition and Redox:Decomposition and Redox:At the conclusion of our time together, At the conclusion of our time together,

you should be able to:you should be able to:

1.1. Identify decomposition chemical reactionsIdentify decomposition chemical reactions2.2. Show the change in oxidation numbers for Show the change in oxidation numbers for

this type of reactionthis type of reaction

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Decomposition

Simple Reactions

Synthesis(Combination)

SingleReplacement

DoubleReplacement

Decomposition

Synthesis

SingleReplacement

DoubleReplacement

A B A B+

A BA B +

A BA B +C+ C

A BAB +C+ CD D

Decomposition

Synthesis

SingleReplacement

DoubleReplacement

A B A B+

A BA B +

A BA B +C+ C

A BAB +C+ CD D

2. Decomposition Reactions2. Decomposition Reactions• Decomposition reactionsDecomposition reactions occur when a occur when a

compound breaks up into the elements or compound breaks up into the elements or in a few to simpler compoundsin a few to simpler compounds

• 1 Reactant 1 Reactant Product + Product Product + Product • In general: AB In general: AB A + B A + B• Example: 2 HExample: 2 H22O O 2H 2H22 + O + O22

• Example: 2 HgO Example: 2 HgO

2Hg + O2Hg + O22

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2. Decomposition Reactions2. Decomposition Reactions• For Decomposition reactionsFor Decomposition reactions to to occur occur

we need energy as a catalyst in the form we need energy as a catalyst in the form of:of:

• HeatHeat• LightLight• ElectricityElectricity• Mechanical shockMechanical shock• Or a chemical catalystOr a chemical catalyst

Decomposition ReactionsDecomposition Reactions• Another view of a decomposition reaction:Another view of a decomposition reaction:

Decomposition ExceptionsDecomposition Exceptions

• Carbonates and chlorates are special case Carbonates and chlorates are special case decomposition reactions that do not go to decomposition reactions that do not go to the elements. You should be able to the elements. You should be able to recognize these as decomposition only.recognize these as decomposition only.• Carbonates (COCarbonates (CO33

2-2-) decompose to carbon ) decompose to carbon dioxide and a metal oxidedioxide and a metal oxide

• Example: CaCOExample: CaCO3 3 CO CO22 + CaO + CaO• Chlorates (ClOChlorates (ClO33

--) decompose to oxygen ) decompose to oxygen gas and a metal chloridegas and a metal chloride

• Example: 2 Al(ClOExample: 2 Al(ClO33))3 3 2 AlCl 2 AlCl33 + 9 O + 9 O22

Decomposition ExceptionsDecomposition Exceptions

• Ternary acids will tend to decompose to Ternary acids will tend to decompose to water and the nonmetal oxide.water and the nonmetal oxide.

• Example: HExample: H22SOSO33 H H22O + SOO + SO22• There are other special cases, but we There are other special cases, but we

will not explore those in this classwill not explore those in this class

PracticePractice

• Predict the products. Then, write and Predict the products. Then, write and balance the following decomposition balance the following decomposition reaction equations:reaction equations:

• Solid Lead (IV) oxide decomposesSolid Lead (IV) oxide decomposes PbO PbO2(s) 2(s)

• Aluminum nitride decomposes Aluminum nitride decomposes

AlNAlN(s)(s)

Pb + O2

Al + N2

Practice of Decomposition and RedoxPractice of Decomposition and Redox

• Predict the products, balance the Predict the products, balance the following reactions and following reactions and show the change in show the change in oxidation numbers oxidation numbers ::

HH22OO

HH22 + O + O22

2 H2 H22O O 2 H2 H22 + O + O22

Each H gains 1eEach H gains 1e-- reduction, oxidizing agentreduction, oxidizing agent

Each OEach O loses 2eloses 2e-- oxidation, reducing agentoxidation, reducing agent

What Do Eskimos Get From Sitting On What Do Eskimos Get From Sitting On The Ice too Long?The Ice too Long?

PolaroidsPolaroids

Decomposition and Redox:Decomposition and Redox:Let’s see if you can:Let’s see if you can:

1.1. Identify decomposition chemical reactionsIdentify decomposition chemical reactions2.2. Show the change in oxidation numbers for Show the change in oxidation numbers for

this type of reactionthis type of reaction

PracticePractice

Identify the type of reaction for each of the Identify the type of reaction for each of the following decomposition reactions, and following decomposition reactions, and write the balanced equation:write the balanced equation:

BaCOBaCO3(s)3(s)

NINI3(s) 3(s)

BaO + CO2

N2 + I2 2, 1, 3

Practice of Decomposition and RedoxPractice of Decomposition and Redox

• Predict the products, balance the following Predict the products, balance the following reactions and reactions and show the change in oxidation show the change in oxidation numbersnumbers::

FeO FeO Fe + OFe + O22

2 FeO 2 FeO 2 Fe + O2 Fe + O22

Each Fe(II) gains 2eEach Fe(II) gains 2e-- reduction, oxidizing reduction, oxidizing agentagent

Each OEach O loses 2eloses 2e-- oxidation, reducing oxidation, reducing agentagent

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