Crude Oil + Fuels

Question 1

What are hydrocarbons?

Answer 1

Compounds made from carbon and hydrogen only

Question 2

What is an alkane?

Answer 2

Hydrocarbons with only single C-C bonds
Alkanes are saturated hydrocarbons with single covalent bonds meaning no more hydrogen atoms can be added
It is an homologous series with its general formula and properties
CnH2n+2
Add ethane to bromine water and remains orange

Question 3

What are alkenes?

Answer 3

Alkenes are unsaturated hydrocarbons with only double C=C bonds
It is also an homologous series with the similar general formula and similar properties
CnH2n
Add ethene to bromine water turns colourless

Question 4

List some materials made from oil?

Answer 4

Petrol, plastic, bitumen/road tar

Question 5

What are the features of crude oil?

Answer 5

Non renewable (Finite)
Origins from remains of dead animals and plants that fell to sea floor and covered in mud without oxygen but with heat and pressure over millions of years produced oil

Question 6

What is crude oil?

Answer 6

Large number of different compounds but most only contain hydrogen and carbon - mostly alkanes

Question 7

What are the first 5 alkanes?

Answer 7

Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Pentane C5H12

Question 8

How do you separate the different compounds in crude oil?

Answer 8

Fractional distillation because they have different boiling points
Use a fractionating column

Question 9

How does fractional distillation work?

Answer 9

Hot vapour is pumped into bottom of the column where temperature is the highest
Towards top of column temperature is lower - temperature gradient
Short chains with low boiling points condense at top of column
Longer chains have a much higher boiling point, so condense near bottom of column

Question 10

What are the different uses of fractions?

Answer 10

25C - fuel gases eg camping stove
40C - gasoline for cars
110C - naphtha - chemical feed stock
200C - kerosene for aircraft fuel
300C - diesel for lorry fuel
350C - residue for roads

Question 11

What happens in combustion?

Answer 11

Fuel (hydrocarbon) + oxygen -> carbon dioxide + water - complete combustion
Fuel + oxygen -> carbon monoxide + water - incomplete combustion

Question 12

What is complete combustion?

Answer 12

When there is unlimited supply of oxygen

So the carbon and hydrogen oxidise fully

Question 13

What is incomplete combustion?

Answer 13

Limited supply of oxygen
So carbon becomes CO (carbon monoxide) or just stays as C (soot)
CO is poisonous
C is global dimming/cooling

Question 14

Combustion experiment-

1. Explain why the funnel is upside down?
2. What is the purpose of water pipe?
3. Why is the U-tube surrounded by ice?

Answer 14

1. To direct gases through the apparatus
2. To draw gases through
3. To cool and condense water vapour into liquid water

Question 15

What is the test for carbon dioxide?

What is the test for water?

Answer 15

Limewater starts colourless and goes milky

Anhydrous copper sulphate goes from white to blue

Question 16

How is crude oil separated and how does it work?

Answer 16

Fractional distillation

1. Crude oil heated to turn into gas or liquid
2. Tower hotter at bottom than at top
3. Vapours rise, cool and condense
4. Long chain hydrocarbons at bottom and shorter at top

Question 17

How can you tell if fractions are pure substances or mixtures?

Answer 17

They boil over a range of temperatures so they are mixtures and not substances

Question 18

How does size of the hydrocarbon affect its properties?

Answer 18

Boiling point - small HC have low bpt - big HC have high bpt
Flammability - small HC are easy - big HC harder
Cleanliness of flame - small HC are clean - big HC are smoky
Viscosity - small HC runny - big HC viscose

Question 19

What is a fraction?

Answer 19

A mixture of hydrocarbons with similar number of carbon atoms

Question 20

What is cracking

Why is it important

Answer 20

Short chains hydrocarbons very useful as fuel but can’t get enough from fractional distillation

A thermal decomposition reaction
Heating up long chains to make shorter chains - very high temp
Makes a combination of alkanes and alkenes
Vapours passed over a catalyst Al2O3
Dodecanese-> hexane +ethane+butane

Question 21

What does saturated mean

Answer 21

Hydrocarbon molecules with only single bonds like alkanes

Question 22

What does unsaturated mean

Answer 22

Contain at least one double or triple bond

Question 23

What is an homologous series

Answer 23

Compounds with the same functional group and the same chemical properties

Question 24

What is viscose

Answer 24

Thick sticky consistency between solid and liquid

Question 25

What is volatile

Answer 25

Substance is easily evaporated and has normal temperature