Crude oils and fuels (7.1) (M)

Question 1

What type of resource is crude oil?

Answer 1

A finite resource

Question 2

Where is crude oil found?

Answer 2

in rocks

Question 3

What is physically crude oil?

Answer 3

Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud

+ include ‘a finite resource found in rocks’ and maybe chemical composition

Question 4

What is the chemical composition of crude oil?

Answer 4

a mixture of a very large number of compounds

Question 5

What are most of the oils found in crude oil?

Answer 5

hydrocarbons

Question 6

What are hydrocarbons?

Answer 6

molecules made up of hydrogen and carbon atoms only

Question 7

What makes up most of the hydrocarbons found in crude oil?

Answer 7

alkanes

Question 8

What is the general formula for the homologous series of alkanes?

Answer 8

C_nH_2n+2

Question 9

What are the first four members of the alkanes?

Answer 9

methane (CH₄), ethane (C₂H₆₎, propane (C₃H₈) and butane (C₄H₁₀)

Question 10

What are the two forms alkanes can be represented in? (formula and diagram)

Answer 10

example for ethane

Question 11

What are many hydrocarbons in crude oil may be separated into?

Answer 11

fractions

Question 12

What are fractions?

Answer 12

mixtures of hydrocarbons which contain molecules with a similar number of carbon atoms, separated by fractional distillation

Question 13

What can fractions be processed to do?

Answer 13

produce fuels and feedstock for the petrochemical industry

Question 14

5 needed

What are some fuels produced from crude oil we depend our modern lifestyle on?

Answer 14

• petrol
• diesel oil
• kerosene (jet fuel)
• heavy fuel oil
• liquefied petroleum gases

Question 15

Many useful materials on which modern life depends are produced by what industry?

Answer 15

the petrochemical industry

Question 16

4 needed

What are examples of useful materials on which modern life depends produced the petrochemical industry

Answer 16

solvents, lubricants, polymers, detergents

Question 17

The vast array of natural and synthetic carbon compounds occur due to what?

Answer 17

the ability of carbon atoms to form families of similar compounds

Question 18

Explain how fractional distillation separates crude oil into fractions

Answer 18

• Crude oil enters a tall fractionating column, which is hot at the bottom and gets cooler towards the top
• The crude oil is heated
• to evaporate the hydrocarbons
• vapours from the oil rise through the column
• hydrocarbons condense when cool enough
• at their different boiling points
• and collected as fractions (each fraction has a different boiling point based on the length of the hydrocarbon chain/molecule)
• smaller hydrocarbons collected at top, larger hydrocarbons collected at bottom (longest ones i.e. bitumen will not evaporate and is collected as residue)

Question 19

How do smaller hydrocarbons compare with large hydrocarbons in terms of the properties: boiling point, flammability, viscocity and smokiness of flame?

Answer 19

Smaller hydrocarbons:

• have lower boiling points
• are more flammable
• have a lower viscosity
• the flame is also cleaner (less smoky) - due to higher flammability

Question 20

What does the combustion of hydrocarbon fuels release?

Answer 20

energy

Question 21

What happens to the carbon and hydrogen in the fuels (hydrocarbons) during combustion?

Answer 21

They are oxidised (gain of oxygen)

Question 22

What does the complete combustion of a hydrocarbon produce?

Answer 22

carbon dioxide and water

Question 23

What does combustion require?

Answer 23

heat

Question 24

What is the formula for the complete combustion of ethene?

Answer 24

C₂H₄ + 3O₂ ⇢ 2CO₂ + 2H₂O

Question 25

What is cracking?

Answer 25

the process of breaking down larger, less useful hydrocarbons to produce smaller, more useful molecules

Question 26

What are 2 forms of cracking?

Answer 26

catalytic cracking and steam cracking

Question 27

What are the conditions required for catalytic cracking?

Answer 27

passing large hydrocarbon vapour (may be soaked in ceramic wool) over a hot catalyst (e.g. porous broken pot).

Heat to very high temperature

only bold is necessary

Question 28

What are the conditions required for steam cracking?

Answer 28

mixing large hydrocarbon vapour with steam and heating to a very high temperature

only bold is necessary

Question 29

What are the products of cracking?

Answer 29

alkanes (saturated) and alkenes (unsaturated)

Question 30

What are more reactive, alkanes or alkenes?

Answer 30

alkenes

Question 31

How do you test for an alkene?

Answer 31

Add orange bromine water to hydrocarbon, if it turns colourless, an alkene is present

(alkenes react with bromine water, alkanes do not)

Question 32

Which fuels are in high demand?

Answer 32

small molecules (hydrocarbons)

crude oil contains too many large hydrocarbons and not enough smaller, more useful ones

Question 33

Some of the products of cracking are used as (…) as small molecules (hydrocarbons) are in high demand

Answer 33

fuels

Question 34

2 needed

What are the uses of alkenes?

Answer 34

• produce polymers
• used as starting materials for the production of many other chemicals

Question 35

What is the reaction for the cracking of C₆H₁₄?

Answer 35

C₆H₁₄ ⇢ C₄H₁₀ + C₂H₄

Question 36

Alkenes turn bromine water from (…) to (…)

Answer 36

brown

colourless

• so bromine water is test for alkenes (no affect on alkanes)*
• as alkenes react with bromine by breaking their carbon-carbon double bond*

Question 37

What are two conditions needed for cracking?

Answer 37

• High temperature
• Catalyst or steam

Question 38

Why does cracking take place?

Answer 38

To obtain smaller hydrocarbon molecules

that are in demand

and are more useful/are used as fuels

Question 39

After cracking, a black substance is produced on the bottom of the beaker. What is this and why is it produced?

Answer 39

Soot

produced by incomplete combustion

Question 40

The demand for smaller hydrocarbon fraction high and supply is low, suggest 3 ways to how the oil industry could overcome this problem

Answer 40

• cracking
• use different/lighter crude oils
• development new techniques to use low demand fractions (or hydrocarbons depending on question) as fuels

Question 41

What does volatile mean?

Answer 41

Evaporates easily/quickly