C7 Flashcards
What is a hydrocarbon?
A hydrocarbon is any compound that is formed from hydrogen and carbon atoms only
What are alkanes?
Alkanes are a group of organic compounds that react in a similar way (homologous series) and are saturated compounds (only have single carbon bonds)
What the general formula for alkanes?
Cn H2n+2
What are the first 4 alkanes and their formulas
Methane-CH4
Ethane-C2H6
Propane-C3H8
Butane-C4H10
Why do hydrocarbon properties change?
1) The shorter the hydrocarbon the less viscous (more runny) it is
2) Hydrocarbons with shorter chains are more volatile and flammable
What do the properties of Hydrocarbons affect how they’re used for?
The properties of hydrocarbons affect how they’re used for fuels
What’s the word equation for complete combustion of oxygen?
Hydrocarbon +oxygen —> carbon dioxide + water (+energy)
What does the complete combustion of any hydrocarbon in oxygen release?
lots of energy
During combustion what happens to the carbon and hydrogen?
The carbon and hydrogen are oxidised
What is crude oil?
Crude oil is a finite resource found in rocks and is the remains of an ancient biomass consisting mainly of plankton that was buried in mud.
How do remains turn into crude oil
Over millions of years with high temperature and pressure the remains turn into crude oil
What is crude oil a mixture of?
Crude oil is a mixture of different hydrocarbons (mostly alkanes)
What are the steps to the different compounds in crude oil being separated by fractional distillation
1) The oil is heated until most of it turns into gas. The gases enter a fractionating column.
2) In the column there’s a temperature gradient (hot at the bottom and gets cooler as you go up)
3) The longer hydrocarbons have high boiling points. They condense back into liquids and drain out of the column early on, near the bottom
Shorter hydrocarbons have lower boiling points, they condense and drain out near the top of the column later on (cooler).
Results of fractional distillation?
End up with crude oil mixture separated out into different columns. Each fraction has a mixture of hydrocarbons that all contain a similar number of carbon atoms, so have similar boiling points
What can the fractions be processed to produce and what does this produce?
The fractions can be processed to produce fuels and feedstock for the petrochemical industry to produce polymers, solvents, lubricants and detergents.
What does crude oil provide?
Oil provides the fuels for transport (petrol, diesel, kerosene, heavy fuel oil and LPG)
Why is there such a large variety of products of crude oil?
Crude oil products are organic compounds with carbon atoms and the carbon atoms can bond together to form families of similar compounds, therefore large variety of products
What is cracking?
Cracking is the breaking down of long chain hydrocarbons into shorter more useful molecules
What are products of cracking useful for?
Short chain hydrocarbons are flammable so make good fuels and are in high demand
What type of reaction is cracking?
Cracking is a thermal decomposition reaction- breaking molecules down by heating them.
What are the two types of cracking?
- Catalytic cracking
-Steam cracking
What are the steps of catalytic cracking?
1) Heat long chain hydrocarbons to vaporise them ( turn into a gas)
2)The vapour is passed over a hot powdered aluminium catalyst
3) The long-chain molecules split apart on the surface of the catalyst
What are the steps of steam cracking?
1) Vaporise long chain hydrocarbons
2) Mix them with steam
3) Heat them to a very high temperature
What are alkenes?
Alkenes are hydrocarbons with a double carbon bond
Why are alkenes unsaturated?
Alkenes are unsaturated because they have 2 fewer hydrogens than alkanes with the same number of carbons
What is the general formula for alkenes?
CnH2n
What are the first 4 alkenes and there formulas?
Ethene- C2H4
Propene-C3H6
Butene-C4H8
Pentene-C5H10
What are alkenes used to produce?
Alkenes are used to produce polymers and as starting materials for the productions of many other chemicals.
Why are alkenes reaction (far more than alkanes)?
The C=C bond can open up to make a single bond allowing the two carbon atoms to bond with other atoms.
What happens when you burn alkenes and what is produced?
They undergo incomplete combustion- carbon and carbon monoxide (poisonous gas) are produced as well as carbon dioxide and water.
What does incomplete combustion of alkenes result in?
A smoky yellow flame and less energy being released compared to complete combustion.
What is a functional group?
A functional group is a group of atoms that determines how the molecules typically reacts.