Crude oil

What is crude oil?

It is a mixture of hydrocarbons

Describe the industrial process of fractional distillation separating crude oil into fractions

1. Crude oil is heated in a furnace and the gas is passed into the fractionating column

2. The oil evaporates at a range of temperatures and condenses due to the top of the column is cooler

3. When each hydrocarbon reaches a temperature lower than their boiling point, they condense into a liquid into various fractions

List the name and uses of the main fractions obtained from crude oil

• Refinery gases - domestic heating and cooking

• Gasoline - fuel for cars

• Kerosene - fuel for aircraft

• Diesel - fuel for some cars and trains

• Fuel oil - fuel for large ships and in some power stations

• Bitumen - surface roads and roofs

Describe trend of colour

Darker colour at the bottom, longer molecules

Describe trend of boiling point

The higher the column, the shorter the molecule, the lower the temp of vaporising and condensing, the lower the boiling point

Describe trend of viscosity

The higher the column, the shorter the molecule, the less viscous

What is a fuel?

It is a substance that releases heat when burned

What are the possible products of complete combustion?

• carbon dioxide

• water

What are the possible products of incomplete combustion?

• carbon monoxide

• water

Why is carbon monoxide poisonous?

Carbon monoxide reduces the oxygen carrying capacity of the haemaglobin. The lack of red blood cells lead to breathing difficulties and later death.

What are the products of nitrogen and oxygen can be produced in high temperatures of car engines?

• nitrogen monoxide

• nitrogen dioxide

How does combustion of some impurities in hydrocarbon fuels result in the formation of sulfur dioxide?

When the fuels are burnt, the sulfur is oxidised to form sulfur dioxide

How does sulfur dioxide and oxides of nitrogen contribute to acid rain?

When they are emitted into the atmosphere, they react with rain water to creat H⁺ ions

What is cracking?

It is the process by which longer chain hydrocarbons are split into shorter, more useful hydrocarbons

What type of reaction is cracking

a thermal decomposition reaction

What are the conditions required for cracking?

• Silica/ alumina as a catalyst

• temperature of 600 - 700 'C

What are the expected products of cracking?

• Alkanes

• Alkenes

Why is cracking necessary?

The demand for smaller chained alkanes are greater, however the supply for longer chained alkanes are greater, therefore in need for cracking