fuels Flashcards
organic chem
what is fossil fuel?
Fossil fuels are formed from declayed plants and animals
What are hydrocarbons
Hydrocarbons only contain carbon and hydrogen
What reaction is combustion?What flame does it produce
combustion is a exothermic reaction
two types of combustion:
complete vs incomplete
complete:Fuel+02—->H2O +CO2
blue,smokeless flame(bunsen burner with air-hole fully opened)
incomplete: Fuel +O2—->C /CO +CO2
(yellow and smokier flame,nusen burner with fully partially closed air-hole)
what is crude oil
it is mixture of hydrocarbons and it has a range of tempertaure
why natural gas and crude oil are non-renewable energy soucres
Limitated amounts of these sources
Cannot be replaced quickly enough to keep up with the rate of use
How is crude oil seperated into different hydrocarbons
Petroleum is heated in a furnace until vapourised: the hot vapours are fed into an industrial fractional column.The hot vapours of lighter fractions will rise higher;since the lighter fractions have lower molecular mass it has weaker intermolecular forces of attrction,so it needs low thermal energy to overcome the weak intermolecular forces of attraction so it has lower boiling point.Hence the lighter hydrocarbons condense at the top while the heavier hydrocarbons condense at the bottom
state the fractions from the lightest to the heaviest ?
Liquified petroleum gas–cooking
Petrol(gasoline)—-fuel for cars
naptha–chemical feedstock
kerosene(paraffin) –fuel aircraft
Diesel —fuel for disel engines
Lubricating oil—lubriants(wax)
Bitumen —-road surface
how to conserve crude oil and natural gas
1.Reduce the use of crude oil
Reduce the number of vehicles on the road
ii. Driving smaller cars that consume less fuel
iii. Taking public transport
2.Use laternative soucres
i)solar panels
ii) biofuels
what are biofule explain with an example
Comes from plants or animals and can be replaced relatively quickly after use
○ E.g. ethanol obtained from the fermentation of the sugar in sugarcane plants. As
sugarcane plants can be regrown and replace within a short period of time →
renewable
The process of germination of sugarcane would absorb CO2 during
photosynthesis - offsets the CO2 produced when the bioethanol is burnt
what is the disadvantge of biofuel
However, to produce enough bioethanol for use, a lot of sugarcane plants needs to be planted and transported for treatment. These processes may require the use of fossil fuels or another valuable resources - more CO2 might be produced.
what factor affect the rate of incomplete combustion
1) insufficient supply of oxygen
2)insufficent mixing of oxygen with fuel
3)insuffient time for oxygen to react
4)burning of substances of larger molecular mass,size(more carbon atoms)
relationship between number of carbon and the percentage composition of carbon
the higher percentage of carbon atoms of substance by mass, more incomplete combustion
Why the percentage yeild of ethanol from bioenthoal method is low
Fermentation is an anaerobic process. The presence of oxygen can cause yeast to shift to aerobic respiration, reducing ethanol yield.
