12 - Alkanes Flashcards
What is the general formula for an alkane?
C(n)H(2n+2)
Describe the polarity and intermolecular forces in alkanes.
Non-polar
Form only van der Waals
What are alkanes?
Saturated hydrocarbons.
What is petroleum?
A mixture containing mostly alkane hydrocarbons that can be separated by fractional distillation.
Describe the conditions for thermal cracking.
High (700-1200K) temperature, high pressure (up to 7000kPa/70 atm)
Give the conditions for catalytic cracking.
High but lower temperature (720K), slight pressure, zeolite catalyst.
What does catalytic cracking produce?
Motor fuels and aromatic compounds.
What occurs in thermal cracking?
C-C bonds are broken.
What does thermal cracking produce?
Mostly alkenes.
Where is the fractionating column hottest?
The bottom
Describe the process of fractional distillation. (3)
Crude oil vapourised
Gases enter fractionating column
Gases condense at different points due to their different boiling point
Each fraction is a mixture
Why is cracking done?
Shorter chains are more useful
Alkenes are more reactive and are used a chemical feedstock
What do alkanes completely combust to?
Carbon dioxide + water
What do alkanes incompletely combust to?
Carbon monoxide + C (soot) + water
Why are alkanes used as fuels?
They release high amounts of energy.