cracking Flashcards
what are the 2 key features of alkanes
they have a general formula CnH2n+2
alkanes only have single covalent bonds between the carbon atoms
what length of chain hydrocarbons (long/short) make good fuels and why?
short chain, they are flammable
long chain hydrocarbons aren’t useful for fuels.
why ?
what can we do to solve this
they aren’t flammable
there is a high demand for short chain hydrocarbons
we convert the long chain hydrocarbons to shorter- chain hydrocarbons by cracking
what is cracking
in cracking a long-chain hydrocarbon is broken down to produce smaller more useful molecules
what can we use the product of cracking long-chain hydrocarbons down for?
fuels (eg in cars)
what are the 2 ways we can carry out cracking
catalytic cracking
steam cracking
what is used in catalytic cracking
In catalytic cracking we use high temperature and a catalyst
What is used in steam cracking
In stain cracking we use high temperature and steam
Key features of alkenes
Alkenes have a double covalent bond between two carbon atoms
They are very useful molecules and used to make polymers and as starting materials.
they are more reactive than alkanes
How are alkenes useful molecules
Alkenes are used to make chemicals called polymers.
Alkenes are also used as a starting material for other useful chemicals as well
they are also very reactive which means we can use this to test for alkenes
Describe the test for alkenes
We use bromine water.
If we shake our alkene with bromine water from the bromine water turns colourless (not clear)
What do we use to test for alkenes
Bromine water which is orange
here we are cracking a long chain hydrocarbon into 2 shorter molecules
C25H52—> C20H42 + C_H_
balance this equation
C25H52 —>C20H42 + C5H10
Work out the number of carbon atoms and hydrogen atoms
C40H82—> C__H__ + C7H14
C40H82—> C33H68 + C7H14
