C6.2 Flashcards
What are alkanes
- saturated hydrocarbons (joined by single covalent bonds only)
- unreactive
- made from alkenes + hydrogen
Formula for alkanes
CnH2n+2
What is a homologous series
Same general formula with each successive member differing with CH2
All have same chemical properties
How do alkanes react with air
Combust -
Complete = carbon dioxide and water
Incomplete = carbon monoxide and water
The larger the alkane molecule…
The stronger the intermolecular forces - the higher the boiling point
Crude oil temp gradient
Hot at the bottom + cold at the top
Highest boiling point
Eg, bitumen - will leave at the bottom of the fractionating column
Lowest boiling point…
Will leave the top as gas
What does cracking convert
Large alkanes into smaller alkanes and alkenes
What does cracking involve
Heating oil fractions to a high temperature (600-700) and passing over a hot catalyst of alumina or silica
- these break the covalent bonds
Why are large alkane molecules not useful
High boiling points - do not flow easily - very viscous - difficult to ignite can not be sold as fuels
As the alkanes increases in size
More viscous + higher boiling point
What are alkenes
- unsaturated hydrocarbons (at least 1 carbon to carbon double bond)
Formula for alkenes
CnH2n
Why do alkenes undergo addition reactions
Because of their double bonds
