Chapter 5 Chemical Reactions and Quantities
Types of Reactions Oxidation-Reduction Reactions
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Type of Reactions
Chemical reactions are classified into four general types Combination Decomposition Single Replacement Double Replacement
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Combination (Synthesis)
Two or more elements or simple compounds 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 2HgO
2KClO3
A + B 2Hg + O2
2KCl + 3 O2
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Learning Check R1
Classify the following reactions as 1) combination or 2) decomposition: ___A. H2 + Br2 ___B. Al2(CO3)3 ___C. 4 Al + 3C 2HBr Al2O3 + 3CO2 Al4C3
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Solution R1
Classify the following reactions as 1) combination or 2) decomposition: _1_A. H2 + Br2 _2_B. Al2(CO3)3 _1_C. 4 Al + 3C 2HBr Al2O3 + 3CO2 Al4C3
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Single Replacement
One element takes the place of an element in a reacting compound. A + BC Zn + 2HCl Fe + CuSO4 AB + C ZnCl2 + H2 FeSO4 + Cu
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Double Replacement
Two elements in reactants take the place of each other AB + CD
AgNO3 + NaCl ZnS + 2HCl
AD + CB
AgCl + NaNO3 ZnCl2 + H2S
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Learning Check R2
Classify the following reactions as 1) single replacement 2) double replacement __A. 2Al + 3H2SO4
__B. Na2SO4 + 2AgNO3 __C. 3C + Fe2O3
Al2(SO4)3 + 3H2
Ag2SO4 + 2NaNO3 2Fe + 3CO
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Solution R2
Classify the following reactions as 1) single replacement 2) double replacement 1_A. 2Al + 3H2SO4
2_B. Na2SO4 + 2AgNO3 1_C. 3C + Fe2O3
Al2(SO4)3 + 3H2
Ag2SO4 + 2NaNO3 2Fe + 3CO
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Combustion
A reaction in which a compound (often carbon) reacts with oxygen
C + O2 CH4 + 2O2 CO2 CO2 + 2H2O
C3H8 + 5O2 C6H12O6 + 6O2
3CO2 + 4H2O 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 equation
1 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 OxidizationReduction
Electrons are transferred
Two processes occur Oxidation = Loss of electrons (LEO) Zn Zn2+ + 2eCu Reduction = Gain of electrons (GER) Cu2+ + 2eLecturePLUS Timberlake 99
Balanced Red-Ox Equations
Combine the oxidation and reduction reactions to make
Loss of electrons = Gain of electrons
Zn + Cu2+ + 2eZn + Cu2+
Zn2+ + 2e- + Cu Zn2+ + Cu
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Gain/Loss of Hydrogen
In organic and biological reactions oxidation = 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. __B. __C. Sn Fe3+ + 1eCl2 + 2eSn4+ + 4eFe2+ 2Cl-
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Solution R3
Identify the following as an 1) oxidation or a reduction process: 1_ A. 2_ B. 2_ C. Sn Fe3+ + 1eCl2 + 2eSn4+ + 4eFe2+ 2Cl-
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Learning Check R4
In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction Ag+ + ClAg + Cl A. Which reactant is oxidized 1) Ag+ 2) Cl3) Ag B. Which reactant is reduced? 1) Ag+ 2) Cl3) Cl
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Solution R4
In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction Ag+ + ClAg + Cl A. Which reactant is oxidized 2) ClClCl + eB. Which reactant is reduced? 1) Ag+ Ag+ + eAg
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