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.

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:

• CH4 (g) + 2O2(g) CO2(g) + 2H2O(l)

• These reactions give out heat. The trend is that the more carbons present the more heat produced.

• 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 C3H8 (g) + 3.5O2(g) 3CO(g) + 4H2O(l)

• With even less oxygen, carbon soot is produced.

. 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/hazard-map?gclid=CLGV4M7CmZ4CFUtp4wodUhM0mg

• 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 !!!

Alkanes in the atmosphere

Methane and ethane make up a tiny proportion

of Jupiter's atmosphere

Traces of methane gas (about 0.0001%) occur in the Earth's atmosphere,

The most important commercial sources for alkanes are natural gas and oil. Natural gas contains primarily methane and ethane, with some propane and butane: oil is a mixture of liquid alkanes and other hydrocarbons.