Leaving Cert Chemistry - Fuels & Heats of Reactions

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Crude Oil

Crude Oil is a fossil fuel and formed from the bodies of tiny sea creatures that died millions of years ago

Fractional Distillation

The heating of crude oil and separating the various mixtures on the basis of their boiling points

Different fractions in the fractionating column (8)

Refinery gas, Petrol, Naphtha, Kerosene, Diesel, Lubricating oil, Fuel Oil, Bitumen

Mercaptens

Mercaptens are sulfur compounds that are added to odourless gases such as refinery gases so that gas leaks can be detected.

Octane Number

Octane Number is a measure of a fuels tendency to resist knocking or auto ignition

Octante number 100

2,2,4 trimethylpentane

Octane number 0

Heptane

residue fractions

the fractions that are left over when the more volatile fractions boil off.

Three Residue Fractions

Lubricating Oil, Bitumen and Fuel Oil

auto ignition

The early explosion of the petrol air mixture in the car’s cylinder is auto ignition or ‘knocking’

Effect of auto ignition

the car engine can lose power and the cylinders can be damaged as a result, the pistons vibrate and a metallic noise is heard.

Low Octane Number rating =

shorter alkane chain

High Octane Number =

more branched alkane chain

anti-knock additive

Tetraethyl lead

How do Lead compounds work?

they poison metal catalysts in the catalytic converter which means they can no longer reduce levels of pollutants in exhaust fumes.

Do cyclic compounds have a higher or lower ON than straight chain compounds

Higher

isomerisation

changing straight chain alkanes into their isomers.