Combustion of Alkanes Flashcards
Why are alkanes generally unreactive?
Alkanes have strong C-C and C-H bonds and are non - polar, making them unreactive towards acids, bases, oxidising agents and reducing agents
What are the products of complete combustion?
Carbon dioxide (CO2) and water (H20)
What is incomplete combustion?
Incomplete combustion occurs when there is a limited supply of oxygen, producing carbon monoxide (CO) or carbon (soot) instead of carbon dioxide (CO2)
How does the number of carbon atoms in an alkane affect the energy released during combustion?
The more carbon atoms present, the greater the heat output due to more bonds being broken and formed
What happens when oxygen is extremely limited in combustion?
Carbon (soot) is formed instead of carbon monoxide or carbon dioxide
Why do longer - chain hydrocarbons undergo incomplete combustion more easily than shorter chains?
Longer - chain hydrocarbons require more oxygen to burn completely, making them more prone to incomplete combustion in limited oxygen conditions
What poisonous gas is produced during incomplete combustion?
Carbon monoxide is produced which binds to haemoglobin, reducing oxygen transport in the blood
What are the main polluting products produced when hydrocarbon - based fuels burn?
Carbon monoxide (CO)
Nitrogen oxides (NOx)
Sulfur dioxide (SO2)
Carbon particulates
Unburnt hydrocarbons
Carbon dioxide (CO2)
Water vapour
How is carbon monoxide (CO) produced, and why is it harmful?
CO is produced by incomplete combustion and is poisonous because it binds to haemoglobin, reducing oxygen transport in the blood
How are nitrogen oxides (NOx) formed in petrol engines?
At high temperatures, nitrogen and oxygen in the air react when fuel ignites, forming NO, NO2 and N2O4
What environmental problems do nitrogen oxides (NOx) cause?
They react with water vapour and oxygen to form nitric acid, contributing to acid rain and photochemical smog
How is sulfur dioxide produced and what is its environmental impact?
It is produced from sulfur impurities in crude oil. It reacts with water vapour and oxygen to form sulfuric acid, contributing to acid rain.
What are carbon particulates and what health effects do they have?
Carbon particulates are ting solid carbon particles that can exacerbate asthma and cause cancer
Why is water vapour considered a greenhouse gas?
Water vapour traps heat in the atmosphere, contributing to the greenhouse effect
Why is carbon dioxide considered a pollutant?
CO2 is a greenhouse gas that contributes to global warming and climate change
How do unburnt hydrocarbons contribute to pollution?
They are greenhouse gases and contribute to photochemical smog, which can cause respiratory problems
At what temperature can an internal combustion engine operate, and why is this significant for nitrogen oxides?
Temperatures can exceed 2000 degrees celsius, allowing nitrogen and oxygen to react, forming nitrogen monoxide
What happens to nitrogen monoxide after it is formed in an engine?
It reacts with oxygen to form nitrogen dioxide
How does nitrogen dioxide contribute to acid rain?
Nitrogen dioxide reacts with rainwater and oxygen to from nitric acid, which falls as acid rain
