Combustion of Alkanes
By Scott Robinson
• Alkanes are usually unreactive and
wont react with acids or bases but
they will burn and react with
halogens.
• The shorter chains burn completely in a
plentiful supply of oxygen for example
Methane:
• CH (g) + 2O (g)
CO (g) + 2H O(l)
• These reactions give out heat. The trend is
that the more carbons present the more
heat produced.
4
2
2
2
• With more carbons equalling more heat,
then they are important as fuels.
• Fuels are substances that release heat
energy during combustion.
• They store a large amount of energy for a
small amount of weight.
• Methane – Main component of ‘natural’
gas
• Propane – ‘Camping’ gas
• Butane – ‘Calor’ gas
• In limited oxygen Carbon Monoxide is
produced
• E.G C H (g) + 3.5O (g)
3CO(g) +
4H O(l)
• With even less oxygen, carbon soot is
produced.
3
2
8
2
. Hydrocarbon based fuels derived from crude
oil may produce polluting products when they
burn :
. Carbon Monoxide
. Nitrogen Oxides produced by N12(g) + O2(g)
2NO(g)
. Sulphur Dioxide
. Carbon Particles
. Carbon Dioxide
• Power stations burn coal, or more usually
in the UK, natural gas to produce
electricity. Some chimneys now use
calcium oxide CaO, or limestone, CaCO3,
to absorb the sulfur dioxide. This produces
gypsum, CaSO4, which is used as plaster.
This process is called flue gas
desulfurisation.
• The internal combustion engine produces most
pollutants but sulphur is now removed from
petrol
• Catalytic converters are equipped into exhaust
systems, these reduce the output of pollutants.
• Reactions done in a catalytic converters: 2CO(g)
+ 2NO(g)
N2(g) + 2CO2(g)
• These reactions take place on the surface of the
catalytic converters
• CO2 traps infra-red radiation so that the Earth’s
atmosphere heats up.
• If the atmosphere rises then there will be more
water vapour and therefore more global
warming.
• http://archive.cyark.org/hazardmap?gclid=CLGV4M7CmZ4CFUtp4wodUhM0m
g
• Sun spots are
magnetic zones that
appear on the sun as
dark spots and
increase the sun’s
energy output.
• This is a theory
against the rising CO2
levels, however the
sunspots could be
causing increased
levels of CO2.
SUNSPOT !!!