Types of Reactions: Combustion LG: I can recognize and predict products of combustion reactions; I can describe hazards of incomplete combustion

Combustion A combustion reaction occurs when a substance (fuel) burns in oxygen – Typically oxygen is supplied by the air, which is only ~21% oxygen Chemical energy stored in the bonds of a fuel are released as heat and light during combustion

Hydrocarbons Many fuels are organic substances called hydrocarbons; they contain only carbon and hydrogen – Examples: Propane and butane Many fuels contain contaminants such as heavy metals and sulfur compounds that can result in air pollution when these fuels are burned

Complete Combustion of Hydrocarbons Occurs when fuels react with excess oxygen Chemical bonds in the fuel are broken to release the maximum amount of energy The only products are carbon dioxide and water: C 4 H 10(g) + O 2(g)  CO 2(g) + H 2 O (g)

Incomplete Combustion of Hydrocarbons Occurs when the supply of oxygen is limited – Burning a fuel in an enclosed space (using a BBQ or running a car engine in the garage – Flames from incomplete combustion contain “soot”; this is the result of un-reacted carbon Complete (lots of O 2 ): C 7 H 16(l) + O 2(g)  CO 2(g) + H 2 O (g) Incomplete (low O 2 ): C 7 H 16(l) + O 2(g)  CO (g) + H 2 O (g) Incomplete (very low O 2 ): C 7 H 16(l) + O 2(g)  C (s) + CO (g) + CO 2(g) + H 2 O (g)

Problems with Incomplete Combustion Only releases SOME of the energy available in a fuel (as a result, the flame is cooler = yellow/orange); this increases cost of burning fuel Soot particles are toxic to the respiratory tract Carbon monoxide is a colourless, odourless, tasteless gas, and is structurally similar to oxygen and so can attach to our red blood cells…200X better than oxygen

Practice Write the balanced equation (with states) for the complete combustion of liquid octane (C 8 H 18 )

Homework New Text: Pg. 197 # 1-6