2 Combustion

Alkanes readily burn in the presence of oxygen. This combustion of alkanes is highly exothermic, explaining their use as fuels. Complete Combustion C8H18(g) + 12.5 O2 (g) → 8CO2 (g) + 9 H2O(l) Fuel : releases heat energy when burnt Incomplete combustion produces less energy per mole than complete combustion If there is a limited amount of oxygen then incomplete combustion occurs, producing CO (which is very toxic) and/or C (producing a sooty flame) CH4 (g) + 3 / 2 O2 (g) → CO(g) + 2 H2O(l) CH4 (g) + O2 (g) → C(s) + 2 H2O(l) The products of complete combustion are CO2 and H2O. In excess oxygen alkanes will burn with complete combustion Incomplete Combustion Carbon (soot) can cause global dimming- reflection of the sun’s light Hydrocarbons as fuels CO is toxic to humans as CO can from a strong bond with haemoglobin in red blood cells. This is a stronger bond than that made with oxygen and so it prevents the oxygen attaching to the haemoglobin. Carbon monoxide is an highly toxic but odourless gas. It can cause death if it builds up in a enclosed space due to faulty heating appliances.