Fuels and Crude Oils (D)

Question 1

Name each fraction that is collected from top to bottom.

Answer 1

1. Petroleum Gas
2. Petrol/Gasoline
3. Naphtha
4. Kerosene
5. Diesel Oil
6. Lubricating Oil
7. Bitumen

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Question 2

State the changes in properties as you go down from petroleum to bitumen

Answer 2

• melting and boiling points increase
• viscosity increases (the fractions become more viscous = flow less easily).
• density increases
• flammability decreases (the fractions burn less easily & burn with a more smoky flame).
• Molecules are bigger and molecular mass increases

Question 3

Why can ethanol be used as an alternative source to fossil fuel.

Answer 3

Ethanol made from glucose is a renewable fuel. Glucose is obtained from plants which can be regrown and replaced and will not run out.

Question 4

Why is there a competing Uses of Fractions

Answer 4

• Some fractions can act as a fuel e.g. petrol, kerosene, diesel oil. They can be burnt to produce energy.
• Some other fractions e.g. naphtha can act as a fuel but also use as common starting materials for the synthesis of other chemicals such as plastics.
• The different uses are competing for the non-renewable supplies of crude oil. The supplies of crude oil are limited. Should we continue to burn the fractions to produce energy, or use them to make other useful materials?

Question 5

How can Crude Oil be Separated into Useful Fractions at Oil Refinery?

Answer 5

1. Crude oil is first heated in a furnace at 400ºC. All hydrocarbons turn into vapour and is passed into the fractionating column.
2. As the hot vapour rises, the different vapours cool down and condense at different heights of the column depending on their boiling points.
3. The fractions with higher boiling points (higher molecular mass) are condensed and collected at the lower levels of the fractionating column.
4. The fractions with lower boiling points (lower molecular mass) rise further up the columnbefore they condense and are collected nearer the top of the column.

Question 6

Why is ethanol formed from the fermentation of glucose renewable?

Answer 6

Glucose is obtained from plants which can be regrown and replaced in a short time period and will not run out.

Question 7

Why is ethanol formed by the addition of steam to ethene non-renewable?

Answer 7

Ethene is obtained from crude oil which is finite and will run out.

Question 8

Why is the use ethanol formed from the fermentation of glucose more environmentally sustainable?

Answer 8

• As sugarcane that is used to make ethanol grows, sugarcane takes in carbon dioxide during photosynthesis. This offsets the carbon dioxide produced when the bioethanol is burnt.
• However ethanol made from ethene cannot remove carbon dioxide gas

Question 9

State the uses of petroleum gas to bitumen

Answer 9

• Used as fuel for cooking and heating
• Used for as fuel for car engines
• Used as chemical feedstock for the petrochemical industry
• Used as fuel for aircraft engines
• Used as fuel for diesel engines such as buses and trains
• for making waxes and polishes
• for making road surfaces