Alkanes
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Describe fractional distillation.
1)Heat the crude oil to vaporise the hydrocarbon mixture. 2)The vapours enter the fractionating column with higher temperatures at the bottom and lower temperatures at the top. 3)As the hot vapours rise through the column, they condense at different heights. 4)The heavy fractions collect at the bottom.
What does the separation of hydrocarbons depend on?
The size of molecules.
The larger the molecule the larger the _______
Van der waal forces.
What is cracking?
The conversion of large hydrocarbons into smaller hydrocarbons by breaking C-C bonds.
Give 2 economic reasons for cracking.
1)The petroleum fractions with shorter carbon chains are more in demand than larger fractions. 2)The products of cracking are more valuable than the starting materials.
Why does cracking require high temperatures?
it is a chemical process that involves the splitting of strong covalent bonds so it requires high temperatures.
What are the two types of cracking?
Thermal Catalytic
What conditions are needed for thermal cracking?
High pressure High Temperature
What does thermal cracking produce?
Mostly alkenes and sometimes hydrogen.
What conditions are needed for catalytic cracking?
Moderate pressure High temperature Zeolite Catalyst
What is produced from catalytic cracking?
Branched and cyclic alkanes and aromatic hydrocarbons.
Why is catalytic cracking cheaper than thermal cracking?
CC saves energy as lower temperatures and lower pressures are used.
What is fuel?
Releases energy when burnt.
Is combustion exothermic or endothermic?
Exothermic.
What is complete combustion?
In excess oxygen, alkanes will burn with complete combustion.
What are the products of complete combustion?
CO2 and H2O
What is incomplete combustion?
If there is a limited amount of oxygen, then incomplete combustion occurs.
What are the products of incomplete combustion?
CO and H2O or C and H2O
What is the difference between incomplete and complete combustion?
Incomplete combustion produces less energy per mole than complete combustion.
What is carbon also known as?
Soot
What can soot cause?
Global dimming - the reflection of the sun’s light.
What is found in petroleum fractions that is damaging?
Sulfur containing impurities which produce SO2 when burned.
What is coal high in?
Sulfur content.
How is acid rain produced?
SO2 dissolves in atmospheric water to produce acid rain.