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Types of Chemical
Reactions
Combustion
• A substance reacts with oxygen to produce an “oxide”. For
example, the burning of gasoline, rusting of iron (iron oxide), and
tarnishing of silver (silver oxide).
Match + Oxygen  Oxide + Energy (heat)
• The most common fuels we burn are called hydrocarbons (a vast
number of compounds containing hydrogen and carbon). Examples
of hydrocarbons are: gasoline, kerosene, candles, matches, and
natural gas.
• If there is sufficient oxygen the products of combusting
hydrocarbons are carbon dioxide and water vapour.
Synthesis
• Atoms or molecules join together to produce a larger molecule.
For Example:
Gasoline + Oxygen  Carbon Dioxide + Water
(sufficient)
• If there is insufficient oxygen the products of combustion
are carbon dioxide, water vapour, carbon (soot), and carbon
monoxide. Carbon monoxide is an odourless and colourless
gas and is very poisonous.
Decomposition
• Larger molecules are broken down into smaller molecules or
atoms.
AB  A + B
A + B  AB
For Example:
Fe(s) + O2(g)  Fe2O3(s)
(skeletal equation)
4Fe(s) + 3O2(g)  2Fe2O3(s) (balanced equation)
Single Displacement
• One atom or group of atoms in a molecule is replaced by
another atom or group of atoms.
A + BC  AC + B
For Example:
H2CO3(aq)  H2O(l) + CO2(g)
2HgO(s)  2Hg(l) + O2(g)
For Example:
Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
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The Metal Activity Series
• The more reactive metals are at the top of the
activity series and the less reactive metals are at
the bottom. A reactive metal will displace or
replace any metal in a compound that is below it in
the activity series.
• You can use the activity series to help you predict
the products of the reaction of a metal and a
metal-containing compound.
Example One:
Fe(s) + CuSO4(aq) 
• You can see from the activity series that iron is above copper. This
means that iron is more reactive than copper. This reaction will
proceed as follows:
Fe(s) + CuSO4(aq)  FeSO4(aq) + Cu(s)
Example Two:
Ag(s) + CaCl2(aq) 
• Silver is below calcium in the activity series, meaning that it is less
reactive. There would be no reaction between these two substances.
Double Displacement
• This involves the joint exchange of atoms or groups of atoms
from one molecule to another.
AB + CD  AD + CB
For Example:
NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(l)
BaCl2(aq) + (NH4)2SO4(aq)  BaSO4(s) + 2 NH4Cl(aq)
Example One: Production of Carbon Dioxide Gas
Na2CO3(aq) + 2HCl(aq)  2NaCl(aq) + H2CO3(aq)
Double Displacement Reactions that
Produce a Gas
• There are three products that indicate that a double
displacement reaction has occurred:
• A solid (precipitate – insoluble)
• Water
• A Gas
• In certain cases, you know that a double displacement
reaction has occurred because a gas is produced.
• The gas is formed when one of the products of the double
displacement reaction decomposes to give water and a gas.
• Example Two: Production of Ammonia Gas
NH4Cl(aq) + NaOH(aq)  NH4OH(aq) + NaCl(aq)
Ammonium Hydroxide
Carbonic Acid
• The carbonic acid is unstable, and as a result,
decomposes to carbon dioxide and water!
H2CO3(aq)  H2O(l) + CO2(g)
• The ammonium hydroxide immediately decomposes to give
ammonia and water!
NH4OH(aq)  H2O(l) + NH3(g)
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Reactions that Involve Metal and Non-Metal Oxides
Forming of non-metal oxides:
• Non-metals will react with oxygen to form non-metal oxides.
• Whether an element is a metal or a non-metal will determine its ability to form an
acid or a base.
N2(g) + O2(g)  2NO2(g)
Forming of metal oxides:
• Metals react with oxygen to form metal oxides.
S(s) + O2(g)  SO2(g)
C(s) + O2(g)  CO2(g)
2Mg(s) + O2(g)  2MgO(s)
4K(s) + O2(g)  2K2O(s)
• When these oxides are exposed to water, they will form a base.
• When these oxides are exposed to water, they will form an acid.
2NO2(g) + H2O(l)  2HNO3(aq) + NO(g)
MgO(s) + H2O(l)  Mg(OH)2(aq)
SO2(g) + H2O(l)  H2SO4(aq) + H2(g)
K2O(s) + H2O(l)  2KOH(aq)
CO2(g) + H2O(l)  H2CO3(aq)
• Alkali metals and alkaline earth metals both follow the same pattern.
Recall: Formulas for Acids and Bases
How to Recognize an Acid:
• Formulas for common acids begin with a hydrogen atom.
• This is how acid rain forms: oxides of nitrogen, sulfur, and
carbon are produced during industrial processes involving
incomplete combustion. These non-metal oxides are released
into the air and react with the water vapour (clouds). The
resulting acidic water then gets released with precipitation
and into our waterways.
Binary acids contain hydrogen and another element.
For Example:
• HCl (Hydrochloric Acid)
• HBr (Hydrobromic Acid)
Oxyacids contain hydrogen and more than one other element.
For Example:
• H2SO4 (Sulfuric Acid)
• H3PO4 (Phosphoric Acid)
How to Recognize a Base:
• Most formulas contain a metal and the hydroxide ion (OH-)
or the bicarbonate ion (HCO3-).
For Example:
• NaOH (Sodium Hydroxide)
• KHCO3 (Potassium Bicarbonate)
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