types of chemical reactions part 3. types of reactions synthesis reactions decomposition reactions...
TRANSCRIPT
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
HydrocarbonsHydrocarbons (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)