Why does petrol have a lower boiling point than fuel oil?

Question

Why does petrol have a lower boiling point than fuel oil?

Answer 1

Petrol as a molecule is a smaller size which means there are less intermolecular forces (e.g van der vaal's forces etc) to overcome than in fuel oil. i.e petrol has a smaller C-C (carbon to carbon) chain than fuel oil.

This means less energy is required to overcome the forces in petrol between the molecules  and therefore a lower boiling point.

Hope that makes sense :)

Answer 2

The hydrocarbon molecules of petrol consist of shorter chain molecules that are therefore 'lighter' than those of Fuel oils.

Petrol consists of 5 to 12 carbons in their chain and are mainly Alkanes and Cyclo-Alkanes with some Aromatics and other Cyclic compounds.



The 'Boiling Range' of Petrol is between an Initial B.P. of around 40°C to a Final B.P. of around 205°C.

The Heavier fuel oil fractions consist of 12 to 20 carbons with a boiling range of  250 to 350°C.

Between Petrol and Fuel oil, we have the fraction called Kerosine, like a light Diesel fuel. A highly refined form of Kerosine is 'Jet Fuel' which is 10 to 18 carbons in the chains and, its boiling range is 175 to 325°C.

Answer 3

Petrol and and Fuel Oil comes from oil which is made up of hydro-carbons. By fractional distillation you break up the the chains of hydrocarbons. The shorter the chain the greater the heat is was exposed to. The longer chains have a higher boiling point as there are many bonds in chain. The shorter take less. The is the same for flamibility.  

Answer 4

Because it has a shorter carbon-hydrogen backbone.

shorter C-H chains are weaker and will break down at lower temperatures.