The Amount of Carbon Dioxide Produced When Fuels Burn (DP IB Chemistry): Revision Note

The Amount of Carbon Dioxide Produced When Fuels Burn

Fossil fuels

What is a fossil fuel?

• Fossil fuels include coal, oil, and natural gas

• They are made of hydrocarbons

• Formed millions of years ago from the remains of dead plants and animals buried in the Earth's crust

• Fossil fuels are non-renewable or finite, they cannot be replaced quickly once used

Advantages of fossil fuels

Coal

• Cheap and widely available

• Long-lasting (longer lifespan than other fossil fuels)

• Can be converted into liquid and gaseous fuels

• Safe to store and handle

• By-products can be useful (e.g. ash used in road construction)

Oil

• Easy to store and transport via pipelines and tankers

• Impurities can be easily removed

• High energy density (releases a lot of energy per kg)

• Easily processed:

  • Can be separated by fractional distillation

  • Cracking produces useful smaller hydrocarbons like alkanes and alkenes

Natural gas

• Cheapest fossil fuel

• Easy to store and transport in pipelines and pressurised containers

• High specific energy (releases large amounts of energy per unit mass)

• Relatively clean:

  • Burns with a blue flame

  • Produces minimal harmful emissions

  • Does not contribute to acid rain

Disadvantages of fossil fuels

• All fossil fuels have limited lifespans / supplies, i.e. are finite 

Coal

• Pollution from combustion:

  • Releases harmful substances:

    • Carbon dioxide contributes to global warming

    • Sulfur dioxide causes acid rain

    • Particulates cause global dimming and visual pollution

• Transport and mining Issues:

  • Difficult to transport

  • Mining causes:

    • Habitat destruction

    • Noise pollution

    • Health risks for miners

    • Safety hazards

• Other concerns:

  • Coal can be slightly radioactive, depending on source

Oil

• Pollution from combustion:

  • Releases:

    • Carbon dioxide contributes to global warming

    • Sulfur dioxide contributes to acid rain

    • Carbon monoxide

• Contributes to:

  • Global dimming / visual pollution

  • Photochemical smog

• Environmental & Safety Concerns:

  • Oil spills harm habitats

  • Drilling poses safety risks

  • Uneven global distribution of oil resources

Natural gas

• Pollution from combustion:

  • Produces carbon dioxide contributes to global warming

• Production and storage Issues:

  • Expensive and time-consuming to extract

  • Difficult and costly to store

  • Safety risks from storing under pressure

Burning fuels

• Many different fuels are used in everyday life

  • The choice of fuel used can depend on:

    • Availability of the fuel

    • Cost

    • Intended use

    • Energy requirements 

• All fuels can undergo combustion to release the chemical energy stored within their bonds 

  • Specific energy is a measure of the energy stored in a substance 

The specific energy of different common fuels

• It is the hydrocarbon contained within the fossil fuel that undergoes combustion

• Remember:

  • Complete combustion of hydrocarbons results in the production of carbon dioxide and water, while incomplete combustion results in the production of carbon monoxide / carbon and water

    • Both types of combustion are exothermic

•  As the length of the hydrocarbon chain increases

  • There is an increased carbon content resulting in the production of more carbon dioxide and carbon monoxide / carbon

  • There are stronger London dispersion forces, which makes the hydrocarbon less volatile

  • The hydrocarbon releases less energy per unit mass of fuel

Graph showing the mass of carbon dioxide and amount of energy released during the combustion of the first eight straight-chain alkanes  

• As the length of the hydrocarbon increases, it is also more likely that incomplete combustion will take place