Organic Chemistry - Crude Oil
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what is crude oil?
a mixture of hydrocarbons
how is crude oil separated?
• crude oil is separated by fractional distillation • crude oil is heated and the oil evaporates. • the gas goes into the fractional distillation tower. as the gas rises the temperature falls. • fractions with higher boiling points condense and are collected nearer the bottom of the tower.
what are the names and uses of the main fractions from crude oil?
from smallest chain length to largest chain length: refinery gases - bottled gas gasoline - fuel for cars kerosene - fuel for aeroplanes diesel oil - fuel for lorries fuel oil - fuel for ships bitumen - road surfacing
what happens to the boiling point of the fractions in crude oil?
the boiling point increases as the number of carbon atoms (chain length) increases
what happens to the viscosity of the fractions in crude oil?
the viscosity increases as the number of carbon atoms (chain length) increases
what happens to the colour of the fractions in crude oil?
the greater the number of carbon atoms (chain length), the darker in colour that fraction is
what happens when fuel is burned?
fuel releases heat energy when burned
what is complete combustion of hydrocarbons?
complete combustion happens when there is enough oxygen available, producing carbon dioxide and water
what is incomplete combustion of hydrocarbons?
incomplete combustion happens when there isn’t enough oxygen available, with possible products being carbon monoxide, carbon, carbon dioxide and water
why is carbon monoxide poisonous?
carbon monoxide is poisonous because it reduces the capacity of the blood to carry oxygen
when are nitrogen oxides formed?
when fuels are burned in vehicle engines, high temperatures are reached. at these high temperatures nitrogen and oxygen from the air react to produce nitrogen oxides
when is sulfur dioxide formed?
fossil fuels such as coal, gas and oil are derived from crude oil. these fuels are hydrocarbons but also include impurities such as sulfur. when the fuels are burned, sulfur dioxide is produced which can escape into the atmosphere
how does sulfur dioxide and oxides of nitrogen oxides contribute to acid rain?
• sulfur dioxide released into the atmosphere from the burning of fossil fuels can react with water and oxygen to make sulfuric acid • also, if sulfur dioxide in the atmosphere reacts with just water, a weaker acid called sulfurous acid is formed • in the atmosphere nitrogen oxides can produce nitric acid
what is cracking?
cracking involves the thermal decomposition of long-chain alkanes into shorter-chain alkanes and alkenes
what conditions are needed for cracking?
temperature: 600C catalyst: aluminium oxide
why is cracking necessary?
• crude oil contains a surplus of long chains • shorter chain hydrocarbons are in greater demand, e.g. petrol • cracking also produces alkenes which are used in making polymers and ethanol