Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

AS HYDROCARBONS AS FUELS

COMBUSTION OF ALKANES

1. Alkanes as fuels

Many of the fractions produced from crude oil are used as fuels. These fractions include:

 

fraction

uses

Liquefied petroleum gases

Camping gas, cooking gas

Petrol

Fuel for cars, motorbikes and machines

Kerosine

Fuel for aeroplanes, lamps, ovens

Diesel

Fuel for lorries, and central heating systems

Fuel oil

Fuel for ships, power stations

Wax

Fuel for candles

 

A fuel is a something that can be changed in a reacting vessel to produce useful energy.

 

Hydrocarbons, and especially alkanes, will react with oxygen in the air to give carbon dioxide and water. A reaction with oxygen is known as combustion. As alkanes are unreactive the reaction needs heat or a spark to get going.

 

These reactions are very exothermic, which means that heat energy is released. This heat energy can be used for direct heating (eg camping gas, central heating, candles). It can also be converted into mechanical energy (eg cars, lorries, ships), or even electrical energy (eg power stations).

 

Typical examples of combustion reactions include:

 

Reaction

 

Enthalpy change/ kJmol-1
CH4 + 2O2 à CO2 + 2H2O -890
C4H10 + 6½O2 à 4CO2 + 5H2O -2877
C8H18+ 12½O2 à 8CO2 + 9H2O -5470

 

The release of heat energy during these combustion reactions results in their widespread use as fuels.

CATALYTIC CONVERTERS