Alkanes Flashcards
What is a hydrocarbon?
A hydrocarbon is a molecule only made of oxygen and hydrogen
Are alkanes hydrocarbons?
Yes
Which type of bonds do alkanes have?
Singular bonds
First 4 alkanes
Methane, Ethane, Propane, Butane (Monkeys Eat Peanut Butter)
Complete combustion equation for hydrocarbons
Hydrocarbon + Oxygen -> Carbon dioxide + Water
When does complete combustion take place?
Only when there is enough oxygen available
What is the equation for the complete combustion of propane?
C3H8 + 5O2 -> 3CO2 + 4H2O
Properties of alkanes
Boiling points increase as molecules get larger, smaller molecules are voletile and highly flammable (good fuels), larger molecules are viscous
During a combustion reaction in alkanes, are the oxygen and hydrogen reduced or oxidised?
Oxidised
Crude oil is mostly made up of hydrocarbons
True
What process is used to seprate crude oil into different substances?
Fractional distillation
What is ‘cracking’ used for?
To break down longer chains of hydrocarbons into shorter ones
2 types of cracking
Catalytic cracking and steam cracking
Explain catalytic cracking
- hydrocarbons are vaporised
- the hydrocarbon vapour is passed over powdered aluminium oxide (catalyst)
- the hydrocarbons split into shorter pieces as they come into contact with the catalyst
Explain steam cracking
- hydrocarbons are vaporised
- the gas is mixed with steam and heated to a high temp
- the hydrocarbons split into shorter pieces
Equation for cracking
Alkane -> Shorter alkane + Alkene
How is an alkane different an alkene
An alkene has 1 double bond, alkanes only have singular bonds
What is a homolgous series?
A group of similar compounds with similar properties
What would you call an alkane?
‘Saturated’ as they only have singular bonds. Alkenes are ‘unsaturated’
Are alkenes more reactive than alkanes?
Yes
What will happen in a reaction between bromine and an alkene?
A solution of alkenes will decolourise orangey-brown bromine water (test for alkenes)
How can alkenes make polymers?
The double bonds can break to form 2 or more bonds
What type of reaction can alkenes undergo?
Addition reaction
How does an addition reaction work?
Carbon double bond opens up and allows 2 other molecules to join
Hydrogenation reaction
- At 150 celsius
- With nickle catalyst
- Reaction with hydrogen and alkene
- Produces alkane
Halogenation reaction
- At room temp
- ## With any halogen and alkene
Hydration reaction
- At 300 celsius
- Phosphoric acid catalyst
- 60 atmospheric pressure
- Produces an alcohol
