COMPLETE AND INCOMPLETE
COMBUSTION
COMPLETE COMBUSTION
• In a combustion reaction, oxygen combines
with another substance and releases energy in
the form of heat and light.
• When oxygen is available in sufficient
amounts complete combustion occurs
COMPLETE COMBUSTION
• This means that all of the carbon
atoms and hydrogen atoms from the
hydrocarbon molecules combine
with oxygen atoms to form carbon
dioxide and water.
• WHAT IS A HYDROCARBON??
– A hydrocarbon is a compound that is composed only of the
elements carbon and hydrogen.
COMPLETE COMBUSTION
• the general equation of the
complete combustion of a
hydrocarbon is:
CxHy + O2 –> CO2 + H2O
CxHy + (4x+y)/4 O2 –> x CO2 + y/2 H2O
COMPLETE COMBUSTION
• Complete combustion is a more efficient
process for generating heat since the flame is
mostly heat and little light.
INCOMPLETE COMBUSTION
• When a reaction has too little
oxygen incomplete combustion is
the result.
• A bright yellow flame is produced during incomplete
combustion. In addition to this, soot and toxic carbon
monoxide can also be formed through incomplete
combustion
INCOMPLETE COMBUSTION
• An example equation of the
incomplete combustion of propane
is:
2C3H 8 (g) + 7O2 (g)  2C(s) + 2CO(g) + 2CO2(g) + 8H2O (g)
INCOMPLETE COMBUSTION
• The products of incomplete combustion
include carbon dioxide and water vapour as
well as carbon, carbon monoxide or both
• Incomplete combustion is a more inefficient
process for generating heat since it has less
oxygen and therefore more light is produced
rather than heat. This will be seen with a
more yellow flame.
Carbon Monoxide
• Why is the formation of carbon monoxide a serious
concern?
Carbon monoxide is a toxic gas that is both colourless and odourless.
Carbon monoxide can bind to oxygen in the blood which will decrease
the number of available oxygen binding sites in a person.
Symptoms of carbon monoxide poisoning include headache, dizziness,
and nausea. Eventually suffocation can be a result of carbon monoxide
poisoning.
Proper ventilation and the use of carbon monoxide detectors in the
home can help to prevent carbon monoxide poisoning.
- If you were in a location where carbon monoxide is being produced. Where
is the safest place to be in relation to carbon monoxide ie how does it
distribute itself through an area?
Complete and Incomplete Combustion
using Propane
• Propane + oxygen  carbon dioxide + water
C3H8 (g) + 5 O2  3 CO2 + 4 H2O
• Propane + oxygen  carbon + carbon dioxide
+ water
C3H8 (g) + 3 ½ O2  1 ½ C + 1 ½ CO2 + 4 H2O
• Oxygen is limited and therefore carbon is
produced as a result.
COMPLETE AND INCOMPLETE
COMBUSTION
• Since incomplete combustion occurs when
there is not enough oxygen. Design an
experiment where you can test this
hypothesis.
• We will be looking into this further in next
Wednesdays lab.
Practice Problems
• What is a hydrocarbon?
• Why is incomplete combustion potentially
hazardous?
• What types of energy do combustion
reactions release?
• Write a balanced chemical equation for the
complete combustion of heptane, C7H16.
• p. 114 - 117, Q 1-3 p. 117
• P. 121, Q 4&5
Practice Problems
• p. 137-141, Q 19-23 p. 140 & Q Q 41-50 p.
141