Incomplete Combustion Flashcards
When does incomplete combustion happen?
when the supply of oxygen to a burning fuel is limited/not enough
when appliances are not well ventilated
What happens during complete combustion of a hydrocarbon fuel?
- hydrogen is oxidised to water vapour, H₂O
- carbon is oxidised to carbon dioxide, CO₂
- energy is given out (more than incomplete combustion)
- the energy is transferred to the surroundings by radiation as light and thermal energy
(oxidised = reacted with oxygen to form…)
What happens during incomplete combustion?
- hydrogen is oxidised to water vapour
- carbon is partially oxidised to carbon monoxide, CO
- carbon is released as carbon particles or soot
- less energy than complete combustion is given out
- the energy is light and thermal
(oxidised = reacted with oxygen to form…)
When does complete combustion happen?
when there is plenty/enough oxygen
e.g. methane + oxygen → carbon dioxide + water
Can carbon dioxide still form during incomplete combustion and why?
yes
the amounts of the different carbon products depend on the oxygen available
(if more oxygen is present carbon dioxide will form)
What type of combustion always happens in vehicle engines?
incomplete combustion
What type of combustion do boilers do when working normally?
complete combustion
Explain why soot/carbon is a problem
carbon is also known as soot
soot can block pipes/jets in gas boilers
it can cause breathing problems and damage lungs if inhaled
it also makes things dirty/blackens buildings
Explain why soot and carbon monoxide are produced during incomplete combustion of a hydrocarbon fuel
- there is a poor supply of oxygen/air, so
- carbon in the fuel is only partially oxidised/reacted to and forms carbon monoxide
- carbon is also released as carbon particles/soot
Explain why carbon monoxide is dangerous
carbon monoxide is difficult to detect, as it is odourless and colourless
it is a toxic gas that causes unconsciousness or death
this is because it binds to haemoglobin in red blood cells, stopping oxygen from binding and reducing the bloods ability to carry oxygen around the body
Explain why carbon dioxide is problematic
carbon dioxide is a greenhouse gas
it contributes to global warming
What are carbon particles also known as?
soot
Explain why water vapour can be a problem
it can cause condensation inside houses, making them damp and possibly leading to mould
Explain how carbon monoxide behaves as a toxic gas
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/prevents oxygen being carried around the body
Describe two problems caused by soot
Soot can build up in chimneys where it can eventually cause fires, it also blackens buildings
Explain why carbon monoxide is difficult for our bodies to detect
it is odourless and colourless
A householder sees soot marks around his gas boiler. He thinks that carbon monoxide is being produced.
Comment on the accuracy of this thought.
Soot shows that incomplete combustion is happening
Carbon monoxide might be forming but soot does not prove this
Carbon monoxide is likely to be forming as well, and can be detected using a carbon monoxide detector
In a 6 mark question about how a good oxygen supply is important, what points do you need to talk about?
- a limited supply of oxygen causes incomplete combustion
- the products of incomplete combustion are dangerous
- the products of incomplete combustion are carbon monoxide, soot/carbon, water and sometimes carbon dioxide
- plenty of oxygen causes complete combustion
- the products of complete combustion are safe
- the products are carbon dioxide and water
- carbon dioxide still is a greenhouse gas and contributes to global warming
- water causes condensation in houses
- carbon monoxide is dangerous because it is odourless and colourless
- this makes it difficult to detect
- it binds to haemoglobin in red blood cells, decreasing the bloods ability to carry oxygen and causing unconsciousness or death
- carbon is released as carbon particles, or soot
- soot blackens buildings
- blocks pipes/jets in boilers
- can cause fires by building up in chimneys
- causes respiratory/breathing problems when breathed in
-Complete combustion:
CⁿH²ⁿ⁺² + O₂ → CO₂ + H₂O
hydrocarbon + oxygen → carbon dioxide + water
-Incomplete combustion:
CⁿH²ⁿ⁺² + O(₂) → CO + C + H₂O (+ CO₂)
hydrocarbon + oxygen → carbon monoxide + carbon + water (+ carbon dioxide)
-Incomplete combustion produces less energy then complete combustion
What are the products of incomplete combustion?
carbon monoxide
carbon
water
sometimes carbon dioxide
Does incomplete combustion produce water?
yes
Name one specific product of incomplete combustion
water
An experiment is set up that tests if a burning candle produces water and carbon dioxide.
The air is pulled through the tubes by a pump.
Boiling tube X is set up after the limewater, it is in a container of water and ice.
Explain why this experiment is not set up correctly, and how it could be proved that the liquid condensing in boiling tube X is water.
Boiling tube X should be swapped with the limewater.
This is so that any water that condenses in boiling tube X is from the candle and not from the limewater.
