4b (Crude oil)

Question 1

What is oil?

Answer 1

Oil is a mixture of hydrocarbons

Question 2

Process of fractional distillation to separate crude oil

Answer 2

• Crude oil is separated by fractional distillation
• Crude oil is heated and the oil evaporates
• The gas goes into the fractional distillation tower. As the gas rises the temperature falls
• Fractions with higher boiling points condense and are collected nearer the bottom of the tower

Question 3

Name and uses of fractions (in order):

Answer 3

-Refinery gases (Bottled gas)
- Gasoline (gasoline for cars)
- Kerosene (Jet Fuel and Paraffin)
- Diesel (fuels)
- Fuel Oil (Fuel for heating and ships)
- Residue / bitumen (for roads and roofing)

Question 4

What is fuel?

Answer 4

A fuel is a substance that, when burned, releases heat energy (exothermic reaction)

Question 5

Complete combustion products

Answer 5

Carbon dioxide and water

Question 6

Incomplete combustion products

Answer 6

Carbon monoxide and water

Question 7

When does complete o incomplete combustion occur?

Answer 7

• Complete combustion occurs when there is enough oxygen available
• Incomplete combustion occurs when there is not enough oxyygen

Question 8

Why is carbon monoxide poisonous?

Answer 8

• Carbon monoxide is produced from incomplete combustion
• It is poisonous becuase it reduces the capacity of the blood to carry oxygen

Question 9

Why do high temperatures are reached in car engines?

Answer 9

• When fuels are burned in vehicle engines, high temperatures are reached.
• At these high temperatures nitrogen and oxygen from the air react to produce nitrogen oxides
• In the atmosphere these nitrogen oxides can combine with water to produce nitric acid (HNO3)

Question 10

How hydrocarbon fuels results in the formation of sulfur dioxide?

Answer 10

• Fossil fuels such as coal, gas and oil are derived from crude oil.
• These fuels are hydrocarbons, but also include impurities such as sulfur.
• When the fuels are burned, sulfur dioxide is produced which can escape into the atmosphere

Question 11

How is acid rain formed?

Answer 11

• Sulphur dioxide in the atmosphere reacts with water (and oxygen(which prouces a stronger acid)) to produce sulphuric acid
• Nitrogen oxide reacts with water and causes nitric acid

Question 12

How long-chain alkanes are converted to alkenes and shorter-chain alkanes
by catalytic cracking

Answer 12

• Cracking involves the thermal decomposition of long-chain alkanes into shorter-chain alkanes and alkenes
• Temperature: 600oC
• Catalyst: aluminium oxide, Al2O3

Question 13

why is cracking necessary?

Answer 13

• Cracking converts long chain hydrocarbons into short chain hydrocarbons.
• Long-chain alkanes are broken down into alkanes and alkenes of shorter length.
• Crude oil contains a surplus long chains.
• Shorter chain hydrocarbons are in greater demand, e.g. petrol.
• Cracking also produces alkenes which are used in making polymers and ethanol.