Unit 2.5 - Crude Oil, Fuels and Organic Chemistry

Question 1

What are hydrocarbons?

Answer 1

Molecules made up of only carbon and hydrogen.

Question 2

What is crude oil?

Answer 2

Crude oil is a complex mixture of hydrocarbons formed over millions of years from the remains of simple marine organisms.

Question 3

What molecules does crude oil contain?

Answer 3

Crude oil contains dozens of hydrocarbons with carbon chains of varying lengths.

Question 4

What happens in a fractioning column?

Answer 4

Crude oil is vaporised/boiled before entering the fractioning column, and the hydrocarbons present in the mixture condense at different temperatures (and hence various heights in the column (the lower the boiling point, the higher up the column the fraction is collected).

Question 5

What is a fraction?

Answer 5

A mixture containing hydrocarbons (alkanes) that have similar boiling points and chain lengths.

Question 6

Name and uses of fraction with lowest boiling point

Answer 6

Petroleum gases - fuel for domestic heating and cooking.

Question 7

Name and uses of fraction with second-lowest boiling point

Answer 7

Petrol/Gasoline - Fuel for cars

Question 8

Name and uses of fraction with third-lowest boiling point

Answer 8

Naptha - Used to make chemicals

Question 9

Name and uses of fraction with fourth-lowest boiling point

Answer 9

Kerosene - Fuel for aircraft

Question 10

Name and uses of fraction with fifth-lowest boiling point

Answer 10

Diesel - Fuel for some cars and trains

Question 11

Name and uses of fraction with sixth-lowest boiling point

Answer 11

Lubricating oil - Used to reduce friction in machinery

Question 12

Name and uses of fraction with seventh-lowest boiling point

Answer 12

Fuel oil - Fuel for ships and power stations

Question 13

Name and uses of fraction with highest boiling point

Answer 13

Bitumen - Used for roads and roofs

Question 14

What 4 trends in properties are there as you go up the fractioning column?

Answer 14

Chain length (decreasing), Boiling point (decreasing), Volatility/Ease of evaporation (increasing) and Flammability (increasing).

Question 15

What other property changes between fractions in the column?

Answer 15

Colour - Bottom fraction is black, middle fractions range from brown-yellow and top fraction is colourless.

Question 16

Describe the social, political and economic importance and impacts of the oil industry. (2)

Answer 16

• Rapidly growing economies (India, China) will use more energy every year and supplying that energy using crude oil is not sustainable in the long term.
• Growing demand or wars in oil producing countries drives prices upwards, affecting individuals’ heating and transport costs, and indirectly causing inflation (e.g. in food prices).

Question 17

Describe the environmental impacts of the oil industry (2).

Answer 17

• Burning fossil fuels releases carbon dioxide into the atmosphere, which contributes to global warming, and releases sulfur dioxide, which causes acid rain.
• Oil spillages can kill thousands of fish and sea birds, and are expensive and difficult to clean up.

Question 18

What difficult decision/choice may have to be made in the future regarding the use of crude oil?

Answer 18

Many important products, such as plastics and medicines, are made using components of crude oil, and so people will eventually have to decide whether to burn the remaining reserves of crude oil or use it for other purposes.

Question 19

What is required and produced in the combustion of hydrocarbons?

Answer 19

The combustion of hydrocarbons requires oxygen (from the air) and produces carbon dioxide and water; it is exothermic and releases useful energy (mostly thermal, but some light energy).

Question 20

Briefly describe an experiment to compare the energy released per gram of different fuels.

Answer 20

1. Measure and record the mass of a spirit burner containing a known alcohol (e.g. methanol, ethanol).
2. Place the spirit burner 2-3cm below a conical flask containing 100cm^3 of water, held in place by a clamp stand.
3. Place a thermometer into the conical flask and measure the starting temperature.
4. Light the spirit burner and allow it to burn until the water temperature has risen by approximately 40C.
5. Record the end temperature of the water and the end mass of the spirit burner and its contents.
6. Repeat steps 1-5 with several other fuels.

Question 21

What is formed in the combustion reaction of hydrogen?

Answer 21

Only water is produced (no carbon dioxide).

Question 22

What are the two main uses of hydrogen as a fuel?

Answer 22

In rocket fuel and in hydrogen fuel cells that are now being used to power cars.

Question 23

Explain the term combustion.

Answer 23

A fuel reacting with oxygen to release useful energy (the reaction is exothermic). Most of the energy released is thermal, some is light energy. When a fuel burns in plenty of air, there is enough oxygen for complete combustion.

Question 24

Explain the advantages of using hydrogen as a fuel.

Answer 24

• Hydrogen is produced from water so it is renewable.

- Water is the only product of the combustion of hydrogen, so does not contribute to global warming or acid rain.

Question 25

Explain the disadvantages of using hydrogen as a fuel.

Answer 25

• It requires large amounts of electricity to produce hydrogen from water via electrolysis (this electricity is expensive to generate).
• Storage of hydrogen requires bulky and heavy pressurised containers and is potentially hazardous as it forms an explosive mixture with air.