Fractional distilaion

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I miss alot of school because i am on chemotherapy, so i am really unsure about crude oil and its uses. i dont understand fractional distillation and i am doing OCR board, can anyone help?  

Posted: 11-04-11 21:44 by Josie

okie dokes, i will give it a shot :)

crude oil is made from the decomposition of ancient animals - more specifically it is a mixture of hydrocarbons (compounds that contain ONLY hydrogen and carbon), the majority of these being alkanes.

Crude oil is separated through fractional distillation - this separates the alkanes based on thier boiling points. Smaller alkanes have weaker inter-molecular forces and therefore lower boiling points. Larger alkanes have stronger intermolecular forces so a higher boiling point.

The crude oil enters the distillation column as a vapour. The column is hottest at its base and cooler at the top. this means that the smallest alkanes will rise to the top to condense because of thier low boiling points and larger alkanes will condense nearer the bottom where it is hotter due to their higher boiling points. from here, the now liquids are siphoned off at the points they have condensed at along the column. They are now called fractions.

The larger fractions which condense at the bottom have high boiling points, do not flow easily, are not very flammable and are not very volatile (not easily vaporised). An example of this is Bitumen, which is heavey-duty and used for roads and roofing.

Lower fractions collected from the top of the collumn are bottled and used in labs for reactions and stuff :)

Is that ok for now?? Just say if you want some more information on the 5 fractions in between these two, but for now i have got cramp in my hand from typing :P

Hope it helped :S 

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Posted: 12-04-11 16:24 by Libby Norman