Incomplete combustion

Question 1

What happens during complete combustion?

Answer 1

During complete combustion of a hydrocarbon fuel, such as petrol, kerosene or diesel oil: hydrogen is oxidised to water vapour, carbon is oxidised to carbon dioxide, and energy is given out (transferred to the surroundings by radiation as heat and light).

Question 2

What happens during incomplete combustion?

Answer 2

During incomplete combustion, hydrogen is still oxidised to water vapour, but: carbon may be partially oxidised to carbon monoxide, carbon may be released as carbon particles or soot and less energy in given out.

Question 3

Why does incomplete combustion happen?

Answer 3

Incomplete combustion happens when the supply of oxygen to a burning fuel is limited.

Question 4

How does carbon monoxide behave as a toxic gas?

Answer 4

Carbon monoxide attaches to haemoglobin in red blood cells, preventing oxygen attaching instead. This reduces the amount of oxygen carried around the body by the bloodstream. Carbon monoxide can cause unonsciousness and even death as it is colourless and odourless.

Question 5

Describe two problems caused by soot?