Transcript Types of Chemical Reactions

Types of Chemical Reactions
Writing Chemical Reactions
Types of Reactions

Many chemical
reactions have
defining
characteristics
which allow
them to be
classified as to
type.
Types of Chemical Reactions

The five types of chemical reactions in this
unit are:
 Combination (Synthesis)
 Decomposition
 Single Replacement
 Double Replacement
 Combustion
Synthesis Reactions
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Two or more substances combine to form
a more complex substance.
 The general form is A + X AX
Example:
 Magnesium + oxygen  magnesium
oxide
 2Mg + O2  2MgO
Magnesium + Oxygen
Synthesis Reactions
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Combination reactions may also be called
composition or synthesis reactions.
Synthesis Reactions
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K + Cl2 
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Write the ions: K+ Cl-
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Balance the charges: KCl
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Balance the equation: 2K + Cl2  2KCl
Decomposition Reactions
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One substance reacts to form two or more
substances.
 The general form is AX  A + X
Example:
 Water can be decomposed by
electrolysis.
 2H2O  2H2 + O2
Electrolysis of Water
Decomposition Reactions
 CaCO3
 CaO + CO2
 H2CO3  H2O + CO2
 Ca(OH)2  CaO + H2O
 2KClO3  2KCl + 3O2
 Zn(ClO3)2  ZnCl2 + 3O2
Single Replacement Reactions
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A metal will replace a metal ion in a
compound.
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The general form is A + BX  AX + B
Single Replacement Reactions
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Examples:
 Ni + AgNO3 
 Nickel replaces the metallic ion Ag+.
 The silver becomes free silver and the
nickel becomes the nickel(II) ion.
 Ni + AgNO3  Ag + Ni(NO3)2
 Balance the equation:
 Ni + 2AgNO3  2Ag + Ni(NO3)
Single Replacement Reactions
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Not all single replacement reactions that
can be written actually happen.
The metal must be more active than the
metal ion.
Aluminum is more active than iron in Al +
Fe2O3 in the following reaction:
Al + Fe2O3 
 Aluminum will replace iron(III) as
was seen in the video.
 Iron(III) becomes Fe and aluminum
metal becomes Al3+.
 2Al + Fe2O3  2Fe + Al2O3
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Double Replacement Reactions
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Ions of two compounds exchange
places with each other.
 The general form is AX + BY  AY
+ BX
Metathesis is an alternate name for
double replacement reactions.
Double Replacement
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NaOH + CuSO4 
The Na+ and Cu2+ switch places.
Na+ combines with SO42- to form Na2SO4.
Cu2+ combines with OH- to form Cu(OH)2
NaOH + CuSO4  Na2SO4 + Cu(OH)2
2NaOH + CuSO4  Na2SO4 + Cu(OH)2
Double Replacement
CuSO4 + Na2CO3 
 Cu2+ combines with CO32- to form
CuCO3.
 Na+ combines with SO42- to form
Na2SO4.
 CuSO4 + Na2CO3  CuCO3 + Na2SO4
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Combustion Reaction
When a substance combines with
oxygen, a combustion reaction
results.
 The combustion reaction may also be
an example of an earlier type such as
2Mg + O2  2MgO.
 The combustion reaction may be
burning of a fuel.
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Combustion Reaction
Methane, CH4, is natural gas.
 When hydrocarbon compounds are
burned in oxygen, the products are
water and carbon dioxide.
 CH4 + O2  CO2 + H2O
 CH4 + 2O2  CO2 + 2H2O
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Combustion Reactions
Combustion reactions involve light
and heat energy released.
 Natural gas, propane, gasoline, etc.
are burned to produce heat energy.
 Most of these organic reactions
produce water and carbon dioxide.
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Practice
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Classify each of the following as to
type:
H2 + Cl2  2HCl
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Combination
Ca + 2H2O  Ca(OH)2 + H2
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Single replacement
Practice
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2CO + O2  2CO2
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Combination and combustion
2KClO3  2KCl + 3O2
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Decomposition
Practice
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FeS + 2HCl  FeCl2 + H2S
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Double replacement
Zn + HCl  ?
Single replacement
 Zn + 2HCl  ZnCl2 + H2
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