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Chemical Reactions and

Quantities

Types of ReactionsOxidation-Reduction Reactions

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Type of Reactions

Chemical reactions are classified intofour general types

zCombination

zDecomposition

z

Single ReplacementzDouble Replacement

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Combination (Synthesis)

Two or more elements or simplecompounds combine to form

(synthesize) one product

 A + B AB

2Mg + O2 2MgO

2Na + Cl2 2NaCl

SO3 + H2O H2SO4

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Decomposition

One substance is broken down (split)into two or more simpler substances.

 AB A + B

2HgO 2Hg + O2

2KClO3 2KCl + 3 O2

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Learning Check R1

Classify the following reactions as1) combination or 2) decomposition:

 ___A. H2 + Br 2 2HBr 

 ___B. Al2(CO3)3  Al2O3 + 3CO2

 ___C. 4 Al + 3C Al4C3

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Solution R1

Classify the following reactions as1) combination or 2) decomposition:

 _ 1 _A. H2 + Br 2 2HBr  _ 2 _B. Al2(CO3)3  Al2O3 + 3CO2

 _ 1 _C. 4 Al + 3C Al4C3

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Single Replacement

One element takes the place of anelement in a reacting compound.

 A + BC AB + C

Zn + 2HCl ZnCl2 + H2

Fe + CuSO4 FeSO4 +Cu

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Double Replacement

Two elements in reactants take the placeof each other 

 AB + CD  AD + CB

 AgNO3 + NaCl  AgCl + NaNO3

ZnS + 2HCl ZnCl2 + H2S

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Learning Check R2

Classify the following reactions as1) single replacement

2) double replacement

 __  A. 2Al + 3H2SO4  Al2(SO4)3 + 3H2

 __B. Na2SO4 + 2AgNO3  Ag2SO4 + 2NaNO3

 __C. 3C + Fe2O

32Fe + 3CO

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Solution R2

Classify the following reactions as1) single replacement

2) double replacement

1 _  A. 2Al + 3H2SO4  Al2(SO4)3 + 3H2

2 _B. Na2SO4 + 2AgNO3  Ag2SO4 + 2NaNO3

1 _C. 3C + Fe2O

32Fe + 3CO

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Combustion

 A reaction in which a compound (oftencarbon) reacts with oxygen

C + O2 CO2

CH4 + 2O2 CO2 + 2H2O

C3H8 + 5O2 3CO2 + 4H2O

C6H12O6 + 6O2 6CO2 + 6H2O

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Learning Check R3

Balance the combustion equation

 ___C5H12 + ___O2  ___CO2 + ___H2O

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Solution R3

Balance the combustion equation1 C5H12 + 8 O2 5 CO2 + 6 H2O

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Oxidation and Reduction

♦

Reactions that involve a loss or gain of electrons

♦Occurs in many of the 4 types of 

reactions and combustion

♦ Important in food metabolism, batteries,

rusting of metals

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Requirements for Oxidization-

Reduction

zElectrons are transferredzTwo processes occur 

Oxidation = Loss of electrons (LEO)

Zn Zn2+ + 2e-

Reduction = Gain of electrons (GER)

Cu2+ + 2e- Cu

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Balanced Red-Ox Equations

Combine the oxidation and reductionreactions to make

Loss of electrons = Gain of electronsZn + Cu2+ + 2e- Zn2+ + 2e- + Cu

Zn + Cu2+ Zn2+ + Cu

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Gain/Loss of Hydrogen

In organic and biological reactionsoxidation = Loss of H

reduction = Gain of H

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Learning Check R3

Identify the following as an 1) oxidation or a reduction process:

 __A. Sn Sn4+ + 4e-

 __B. Fe3+ + 1e- Fe2+

 __C. Cl2

+ 2e- 2Cl-

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Solution R3

Identify the following as an 1) oxidation or a reduction process:

1_ A. Sn Sn4+ + 4e-

2_ B. Fe3+ + 1e- Fe2+

2_ C. Cl2

+ 2e- 2Cl-

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Learning Check R4

In light-sensitive sunglasses, UV lightinitiates an oxidation-reduction reaction

 Ag+ + Cl-  Ag + Cl

 A. Which reactant is oxidized

1) Ag+ 2) Cl- 3) Ag

B. Which reactant is reduced?

1) Ag+ 2) Cl- 3) Cl

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Solution R4

In light-sensitive sunglasses, UV lightinitiates an oxidation-reduction reaction

 Ag+ + Cl-  Ag + Cl

 A. Which reactant is oxidized

2) Cl- Cl- Cl + e-

B. Which reactant is reduced?

1) Ag+  Ag+ + e- Ag