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i need help with my coursework, im really stumped...
i am doing 'which is the best fuel?'
there is : ethanol, methanol, butanol, propanol and hexanol... why is hexanol the best fuel? something to do with molecular structure?
thanks
tom
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Posted: 2006-04-04 18:04:05
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The best fuel is one which has the least oxygen and the maximum hydrocarbon molecules... Its not related to the structure... At all
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Posted: 2006-04-04 18:08:48
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ahh yeah, hexanol then, its the biggerst number of hydro carbons, i got that bit, its just our teacher says abput half a page/ a page for explanation, but i dont see how i can write more than 'i think hexanol is the best fuel as it has the maximum number of hydrocarbons'
thanks for your help dude
oh and is he breakdown of the hydrocarbons called cracking?
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[ This Message was edited by: Glenny on 2006-04-04 17:14 ]
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Posted: 2006-04-04 18:10:24
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answer off my ex:
for the chem i dont actually know properly... could be that the molecule is larger so more CO2 and H2O is released so much energy to run the car... could be as hexanol is a longer molecue it has the ability for cracking isomerisation and reforming to make better fuels (hopefully he knows what those 3 mean lol the c,r and i).
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Posted: 2006-04-04 18:17:56
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so basically hexanol has more hydrocarbon molecules. Cracking gives off heat energy, so more molecules are cracked, giving more heat energy? and not sure bout the r,i
does cracking produce heat? it better do cos ive done the rest of the coursework saying it does :S
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[ This Message was edited by: Glenny on 2006-04-04 17:27 ]
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Posted: 2006-04-04 18:20:29
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Ideally a fuel should not have any oxygen molecules as the OH group just forms a H2O molecule giving nothing useful. However alcohols have good anti-knock properties plus they reduce the reactivity of emission gases(and hence reduce smog).......so alcohols are generally added to pure hydrocarbon fuels. Hexanol is therefore the best of those given as it has an optimum ratio of oxygen:hydrocarbon molecules.
Cracking is the process of splitting large hydrocarbons into smaller more useful ones.....as far as i'm aware it doest produce heat. Infact thermal/catalytic processes are required to bring about the process so heat is used.
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Posted: 2006-04-04 19:49:03
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catalysts just speed up the reaction though? i got this:
i think hexanol is the best fuel as i believe it will heat the water up the most meaning it will produce most heat. if methanol is:
(methanol diagram)
this means less bonds are to be cracked and less heat produced. However, hexanol being:
(hexanol diagram, cant be bothered to write it out)
shows hexanol has alot more bonds. When these are broken, heat energy will be produced. Because there are alot more bonds in hexance, more hear energy will be produced.
you think its good/bad?
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[ This Message was edited by: Glenny on 2006-04-04 19:40 ]
[ This Message was edited by: Glenny on 2006-04-04 19:47 ]
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Posted: 2006-04-04 20:37:27
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Ok dude, you should really pay more attention in your lectures! But here we go, cracking does not produce heat as previously mention, it is only used to break down long hydrocarbons to shorter more useful ones. Isomerisation is where long chain hydrocarbons such as butane into more branched hydrocarbons. Lastly, reformation is where cyclic hydrocarbons are made from chain hydrocarbons
[ This Message was edited by: SE Rules on 2006-04-04 20:12 ]
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Posted: 2006-04-04 20:58:48
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eep... i do listen, its just that this is course were getting from energy topic ? all we;ve being learning is energy in joules and energy transfers, i really dont see how the coursework connects to this... im gonna go see my teacher tomorow, hopefully get it all sorted out...
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Posted: 2006-04-04 21:01:24
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okay, I'm not entirely sure where everyone is coming up with this crap about hexanol being the longest therefore the best. Ask yourself, does methane or hexane burn easier? methane! More bonds to be broken means that more energy must be put in to break them therefore making an inefficient fuel. This would suggest that methanol is the best choice. in practice, ethanol is used as seen in brazil.
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Posted: 2006-04-04 21:23:53
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