PETROLEUM
points.
The aromatic hydrocarbons are unsaturated hydrocarbons which have one or more
planar six-carbon rings called benzene rings, to which hydrogen atoms are attached with
the formula CnHn. They tend to burn with a sooty flame, and many have a sweet aroma.
Some are carcinogenic.
These different molecules are separated by fractional distillation at an oil refinery to
produce petrol, jet fuel, kerosene, and other hydrocarbons. For example, 2,2,4-
trimethylpentane (isooctane), widely used in petrol, has a chemical formula of C8H18
and it reacts with oxygen exothermically:
2 C8H18(l) + 25 O2(g) → 16 CO2(g) + 18 H2O(g) (ΔH = −10.86 MJ/mol of octane)
The amount of various molecules in an oil sample can be determined in laboratory. The
molecules are typically extracted in a solvent, then separated in a gas chromatograph,
and finally determined with a suitable detector, such as a flame ionization detector or a
mass spectrometer
annaabi.ee 
