TYpes of Chemical Reactions
Part 3
Types of REactions
Synthesis Reactions
Decomposition Reactions
Single Displacement Reactions
Double Displacement Reactions
Combustion
Corrosion
combustion
Combustion is the
chemical reaction in
which fuel “burns” or
reacts quickly with
oxygen
The products of this
reaction are usually
an oxide and energy
Sunrise Propane
Explosion
Toronto 2008
Hydrocarbons
Hydrocarbons (HC) are a group of compounds
that only contain the elements carbon and
hydrogen
Example: Propane, C3H8
HC originate from fossil fuels
The combustion of HCs power cars & buses,
warm homes, generate electricity & light candles
Complete combustion of
Hydrocarbons
Products of HC combustion can vary - depend on
availability of oxygen
Plentiful oxygen = complete combustion
Complete combustion of HC:
hydrocarbon + oxygen → CO2 + H2O + energy
CO2 is an important green house gas - more in
climate change unit!
complete combustion of
hydrocarbons
The balanced chemical equation for the complete
combustion of hydrocarbons can be represented
by the general equation:
CxHy + O2 → CO2 + H2O + energy
During complete combustion, fuel burns clean
with no sooty residue
Incomplete combustion of
hydrocarbons
If oxygen supply is limited,
incomplete combustion may
occur
Results in release of carbon
monoxide gas and carbon (soot)
in addition to carbon dioxide and
water
An orange flickering flame
indicates incomplete combustion
Carbon Monoxide (CO)
Carbon monoxide is a colourless, odorless gas
Highly toxic
Symptoms of poisoning - headaches, dizziness,
nausea, respiratory problems
Cause of many deaths - incomplete combustion
in confined space
Carbon monoxide detectors!
soot
Made up of particles of
carbon
Causes pollution and
wastes energy
Common in older
vehicles with poorly
maintained engines
Common result of forest
fires
Other combustion reactions
Many substances (besides HC) undergo
combustion
Elements react with oxygen to form oxides
General equation: element + oxygen → oxide +
energy
Eg. magnesium burns to form magnesium
oxide + energy
Corrosion
Is the breakdown of metal as a result of chemical
reactions with the environment
beneficial corrosion
Example: aluminum exposed to air
Corrodes to form aluminum oxide - one of the
hardest substances known
Aluminum oxide tightly coats underlying metal,
preventing further corrosion
Application - camping pans
rust
Familiar reddish-brown flaky material produced
when metals containing iron corrode
Rust does not stick well to underlying steel
Readily flakes away so fresh steel is exposed to
further corrosion
Continues until steel is completely eaten away!
rust
Causes of rust:
Oxygen
Water
Electrolytes - not a cause, but speeds up
corrosion once it starts
Preventing corrosion
Protective Coatings
Cover metal with rust inhibiting paint, chrome
or plastic coating
Corrosion still possible with chips/scratches
Corrosion resistant materials
Plastic - Eg. car bumpers
Corrosion resistant alloys (blend of metals) Eg. surgical knee implant
Galvanizing
Galvanized steel is steel coated with thin layer of
zinc
Zinc corrodes before steel
Zinc corrodes to form protective oxide layer
Demo of the day!
Time for some combustion in action!
Combustion of acetylene
2C2H2 (g) + 5O2 (g) → 4CO2 (g) + 2H2O(g)