How are various fractions taken from crude oil by fractional distillation.
[4 marks]
Visual Mark Scheme Breakdown
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It is heated in a furnace to vaporise
(1 mark)
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There is a temperature gradient (cool at the top, hot at the bottom)
(1 mark)
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The gases condense a different heights of the column
(1 mark)
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Each gas has a different boiling point and therefore condenses at a different height
(1 mark)
At the cooler top, short-chain hydrocarbons with low boiling point exit
At the hotter bottom, long-chain hydrocarbons with high boiling points exit
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