COMBUSTION OF HYDROCARBONS
HYDROCARBONS
Hydrocarbon molecules are composed of only carbon and hydrogen atoms. When these
molecules have functional groups (e.g. –OH) attached, they are no longer comprised of just
purely carbon and hydrogen, and fall under the blanket of organic compound.
ALIPHATIC HYDROCARBONS
Alkanes: contain single-bonded carbon atoms (CnH2n+2)
Butane
butane
3-ethyl-heptane
Alkenes: contain double-bonded carbon atoms (CnH2n)
2,5-dimethyl-2-hexene
Alkynes: contain triple-bonded atoms (CnH2n-2)
2,6-dimethyl-3-heptyne
AROMATIC HYDROCARBONS
Aromatic hydrocarbons are hydrocarbons with a cyclic structure
COMPLETE COMBUSTION
One property common to all
hydrocarbons is that they are combustible
(they burn). Complete combustion occurs
when the oxygen supply is plentiful.
The general, unbalanced chemical
equation is:
CxHy+O2 (g)🡪 CO2 (g)+ H2O (g) + energy
The carbon-carbon bond, when burned (in oxygen gas) releases energy (as heat, fire).
Combustion of methane (CH4)
CH4 + 2 O2 🡪 CO2 + 2 H2O
Combustion of ethane (C2H6)
Combustion of butyne (C4H6)
INCOMPLETE COMBUSTION
Incomplete combustion occurs when the oxygen supply is limited, which usually
happens in confined spaces, and can lead to a variety of products.
CONCERNS RELATED TO INCOMPLETE COMBUSTION (See pg 194-195)
1) Incomplete combustion only releases a portion of the energy that may be obtained from
hydrocarbon fuels such as gasoline.
2) Soot particles are an inhalation hazard. ( C )
3) Carbon monoxide produced during incomplete combustion in also an inhalation hazard,
and is known as the ‘silent killer’ because is has no odour, taste and is colourless and
causes asphyxiation.