Crude Oil

Question 1

What is crude oil a mixture of?

Answer 1

Hydrocarbons

Question 2

What are fractions of crude oil?

Answer 2

• A group of hydrocarbons which can be extracted from crude oil
• They all have similar properties such as chain length (number of carbon and hydrogen atoms) and boiling point

Question 3

By which process is crude oil seperated into different fraction?

Answer 3

Fractional distillation

Question 4

How does fractional distillation work?

Answer 4

• It is carried out in a fractionating column which is hot at the bottom and cool at the top
• Crude oil enters at the bottom, and is vaporised
• The vapours of hydrocarbons with long-chains and high boiling points will instantly condense to be tapped off
• The vapours of hydrocarbons will condense as they move up the column according to their boiling point, with the short-chain hydrocarbons only condesing once they reach the top due to their low boiling point

Question 5

What are the main fractions of crude oil in order of boiling point and chain-length (lowest to highest)?

Answer 5

• Refinery gas
• Gasoline
• Kerosene
• Diesel
• Fuel oil
• Bitumen

Question 6

What are the uses of refinery gas?

Answer 6

Domestic heating and cooking

Question 7

What are the uses of gasoline?

Answer 7

Fuel for cars

Question 8

What are the uses of kerosene?

Answer 8

Fuel for aircrafts

Question 9

What are the uses of diesel?

Answer 9

Fuel for older cars and other vehicles with diesel engines

Question 10

What are the uses of fuel oil?

Answer 10

Fuel for ships and power stations

Question 11

What are the uses of bitumen?

Answer 11

Surfacing roads and roofs

Question 12

What is the trend in viscosity as you increase chain-length of the hydrocarbons?

Viscosity is the ease of flow of liquid

Answer 12

As chain-length increases, viscocity increases due to the increasing attraction between hydrocarbon molecules

Question 13

What is the trend in colour as you increase chain-length of the hydrocarbons?

Answer 13

As chain-length increases, the colour becomes darker (as viscosity increases)

Question 14

What is the trend in boiling point as you increase chain-length of the hydrocarbons?

Answer 14

As chain-length increases, the boiling point increases due to increasing attraction between hydrcarbon molecules

Question 15

What are the products of complete combustion of a hydrocarbon when there is plentiful oxygen?

Answer 15

• Carbon dioxide and water
• For example: Methane + Oxygen = Carbon dioxide and water

Make sure the equations are balanced and accurate

Question 16

What are the products of incomplete combustion of a hydrocarbon when there is some oxygen?

Answer 16

• Carbon monoxide and water
• For example: Methane + Oxygen = Carbon monoxide and water

Question 17

What are the products of incomplete combustion of a hydrocarbon when there is little oxygen?

Answer 17

• Carbon and water
• For example: Methane + Oxygen = Carbon and water

Question 18

Why is carbon monoxide dangerous?

Answer 18

• It is toxic and odourless so cannot be detected
• It binds very tightly to haemoglobin, disallowing the haemoglobin to carry oxygen or carbon dioxide
• This needs to the body not receiving enough oxygen and there being a build up of carbon dioxide

Question 19

How are oxides of nitrogen formed in a car engine?

Answer 19

• The combustion reaction inside of a car engine provides high amounts of heat energy
• This provides the conditions for oxygen and nitrogen in the air to react and form oxides of nitrogen

Carbon monoxide and unburned hydrocarbons are other toxic substances produced in car engines. These substances are produced through incomplete combustion

Question 20

What do catalyctic converters do and how do they work?

Answer 20

• Catalyctic converts reduce/oxidise toxic gases produced in a combustion engine, rendering them harmless
• They do this by passing the gasses through a honeycomb structure of transition metal catalysts to facilitate these reactions
• Nitrogen oxide is reduced to nitrogen gas, carbon monoxide is oxidised to carbon dioxide and unburned hydrocarbons are oxidised to produce carbon dioxide and water

Question 21

How is sulfur dioxide formed through the combustion of hydrocarbon fuels?

Answer 21

• Some hydrocarbons - espeically coals - contain some sulfuric impurities
• When these fuels are combusted, the sulfur is oxidised to form sulfur dioxide

Question 22

How is acid rain formed?

Answer 22

• Sulfur dioxide and nitrogen dioxide produced by the aforementioned ways in the air dissolve in rainwater to form sulfuric acid and nitrous/nitric acids respecitively
• The acidic droplets fall as rain, resulting in acid rain

These gases can also result in photochemical smog

Question 23

What does cracking break down into what?

Answer 23

• Long chain alkanes are broken down into alkenes and shorter chain alkanes (and sometimes hydrogen)
• For example, Decane –> Octane + Ethene

Make sure the equation is balanced

Question 24

What are the conditions required for catalyctic cracking to occur?

Catalytic cracking is just the normal method of cracking

Answer 24

• 600-700 degrees celcius temperatures
• Under the presence of an aluminium oxide (aluminia) or silicon dioxide (silica) catalyst

Question 25

Why is cracking important?

Answer 25

• The demand for the smaller fractions of crude oil is higher than their supply, but the opposite is true for the larger fractions
• Therefore larger fractions such as fuel oil which are less useful are cracked into more useful smaller fractions such as ethene which can be used for form polymers
• Smaller chain alkanes can be used as fuel for vehicles and the alkenes can be used to make alcohol