Why do different fractions form from fractional distillation?

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SUMMARY

The discussion focuses on the phenomenon of overlapping carbon chain lengths in fractions obtained from fractional distillation, specifically highlighting petrol (C4-C12), naptha (C7-C14), and kerosine (C11-C15). Despite their similar carbon lengths, these fractions boil at distinct temperature ranges: petrol at 40-100°C, naptha at 100-150°C, and kerosine at 150-250°C. The key conclusion is that boiling points are influenced not only by the number of carbon atoms but also by the molecular structure, including whether the chains are straight or branched. This structural variation is critical in understanding the separation of these fractions.

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Cheman
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Fractions of distillation...

Some of the fractions which result from fractional distillation seem to share carbons of the same length - yet these form different fractions. Why?

Eg - Petrol is carbon chain length 4 - 12, naptha is 7 - 14 and kerosine is 11 -15; why the overlap when they boil at very distinct temps. ie - petrol 40 - 100, naptha is 100 - 150 and kerosine is 150 - 250 degrees C.

Thanks. :smile:
 
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Cheman said:
Some of the fractions which result from fractional distillation seem to share carbons of the same length - yet these form different fractions. Why?

Eg - Petrol is carbon chain length 4 - 12, naptha is 7 - 14 and kerosine is 11 -15; why the overlap when they boil at very distinct temps. ie - petrol 40 - 100, naptha is 100 - 150 and kerosine is 150 - 250 degrees C.

The simplest answer will be that boiling point depends not only on number of carbons, but also on the chain structure - whether it is straight or branched.


Chemical calculators for labs and education
BATE - pH calculations, titration curves, hydrolisis
 
"Distillation" --- evaporation of a MIXTURE. Do a few calculations of liquid and vapor compositions that are at equilibrium at the temperatures bounding the fractions you've listed.
 

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