Hydrocarbons Flashcards
What is a hydrocarbon?
Any compound made of hydrogen and carbon only
What is an Alkane?
The simplest hydrocarbon
Homologous series (organic compounds that react in a certain way)
Saturated compounds
MEPB
Hydrocarbons chains properties
shorter = less viscous (runny), lower boiling points, more flammable
longer = more viscous (runny), higher boilings points, less flammable
Complete combustion with a hydrocarbon
hydrocarbon + Oxygen = Carbon dioxide + water (+energy)
What is fractional distillation?
The Crude Oil is heated and separated based on boiling points using a fractioning column
What is crude oil?
A fossil fuel formed from the remains of plants and animals
How does a fractionating column work?
Crude oil is heated to almost evaporating and enters the fractional column, where there is a temperature gradient. The longer hydrocarbons condense at the bottom due to higher boiling points
The crude oil separates into different fractions with similar numbers of carbon atoms and similar boiling points
Uses of crude oil
Fuel for modern transport (e.g. cars, planes)
Petrochemical industry uses hydrocarbons in things like solvents, lubricants or polymers
All products from crude oil are examples of organic compounds
What is cracking?
Splitting long chain hydrocarbons by heating them
Why do we do cracking?
Short chain hydrocarbons are flammable so good fuels and high in demand
Long chain hydrocarbons are thick liquids like tar
Produces alkenes which are the starting material for other compounds and polymers
Some products are useful as fuels
Name the different methods of cracking
Catalytic cracking
Steam cracking
What is Catalytic cracking?
The long chain hydrocarbon is heated to a high temperature to produce smaller chain alkenes and alkanes using a catalyst
What is steam cracking?
The long chain hydrocarbon is heated to a high temperature to produce smaller chain alkenes and alkanes. The alkane vapours mix with the steam
What are alkenes?
Hydrocarbons which have a double bond between two of the carbons in their chain. They are unsaturated (as they include a double bond). They are reactive as the double bond can open up to bond with other atoms
Alkenes and combustion
With enough oxygen they combust completely to produce only water and carbon dioxide
If there isnt enough oxygen, when they burn they can produce carbon monoxide and produce a smoky yellow flame.
What colour is the alkene incomplete combustion flame?
Smokey yellow
Addition Reactions
Majority of reactions occur by addition reactions
The carbon-carbon double bond will open up and a new atom is added
Hydrogeneration reaction
Hydrogen reacts with the double bonded carbons to open the double bond and form a saturated alkane in the presence of a catalyst
Steam react with alkene
when alkenes react with steam, water is added to the double bonds and an alcohol is formed.
Halogens react with alkenes
Alkenes will also react in addition reactions with halogens to form saturated molecules as the halogen breaks the double bond and replaces it.
