Cracking and Alkenes Flashcards
Why do we use cracking?
the shorter hydrocarbon chains that are separated from fractional distillation and useful because they are flammable and good fuels however the longer ones aren’t as useful because they are thick viscous liquids. so we can break them down into shorter ones by cracking. they also are necessary to increase supple of fuels that are in high demand
What is cracking?
breaking down long chain hydrocarbons into shorter ones by heating them. its a thermal decomposition reaction
What are the two types of cracking?
catalytic cracking and steam cracking
What are the steps for catalytic cracking?
- heat up long chain hydrocarbons and vapourise them (turn into gas)
- gas comes into contact with hot powdered aluminium oxide (catalyst) which splits them apart into 2 smaller hydrocarbons
What are the steps for steam cracking?
- heat up long chain hydrocarbons and vapourise them (turn into gas)
- mix gas with steam and heat to a very high temperature causing the long hydrocarbons to split apart into shorter ones
What happens in cracking?
the long chain alkane splits into a short chain alkane and a alkene
the number of carbons on each side will stay the same however the alkene has a double bond
What can alkenes be used for?
instead of waste products they can be used to produce polymers and other materials
What are alkenes?
another homologous series of hydrocarbons with a carbon to carbon double bond
What is the general formula for alkenes?
CnH2n
What is saturated and unsaturated?
saturated: only single bonds (alkanes)
unsaturated: double bonds (alkenes)
What happens to bromine water when reacted with alkenes?
if you add alkenes to a solution of bromine water it will turn it from orange to colourless, it will decolourise it
