Chapter 4 - Crude Oil And Fuels

Question 1

What are most of the compounds in crude oil

Answer 1

Hyrdrocarbons

Question 2

What is a hydrocarbon

Answer 2

Molecules that contain only hydrogen and carbon

Question 3

What is the general formula of an alkane

Answer 3

CnH2n+2

Question 4

What is an alkane

Answer 4

A saturated hydrocarbon as it contains only single carbon - carbon bonds and do not contain any c=c double bonds.

Question 5

How does the boiling point of a hydrocarbon depend on the size of its molecule

Answer 5

The larger the molecule, the higher the boiling point of the hydrocarbon

Question 6

Describe process of fractional distillation

Answer 6

• Crude oil is vaporised and fed into a fractionating column. It is hot at the bottom and gets cooler going up the column
• There are many trays with holes to allow gases through. The hydrocarbons condense to liquids when they reach the level that is at their boiling point
• Hydrocarbons with the smallest molecules have the lowest boiling points and so are collected at the top of the column. The fractions at the bottom of the column contain hydrocarbons with the highest boiling points.

Question 7

What does viscosity mean

Answer 7

How runny a liquid is. Fractions with low boiling ranges have low viscosity so are runny liquids.

Question 8

What are the features of fractions with low boiling ranges

Answer 8

They are very flammable so that ignite easily. They also burn with a clean flame, producing little smoke which makes them very useful as fuels

Question 9

What happens when pure hydrocarbons burn completely

Answer 9

They are oxidised to carbon dioxide and water

Question 10

What is incomplete combustion and what is produced

Answer 10

When there is a limited supply of oxygen. Carbon monoxide is produced. Carbon may also be produced and some of the hydrocarbons may not burn. This produces solid particles that contain soot and unburnt hydrocarbons called particulates.

Question 11

What causes acid rain

Answer 11

Sulphur dioxide

Question 12

What other substance causes acid rain

Answer 12

Nitrogen oxides

Question 13

What is global dimming

Answer 13

Tiny solid particulates that reflect sunlight

Question 14

How does sulphur dioxide produce acid rain

Answer 14

The gas dissolves in water droplets and reacts with oxygen in the air to produce acid rain

Question 15

How do we remove harmful substances from waste gases before they are released into the atmosphere

Answer 15

Sulphur dioxide is removed from the waste gases of power stations. Exhaust systems of cars are fitted with catalytic converters to remove carbon monoxide and nitrogen oxides. Filters can remove particulates. Sulphur can be removed from fuels before they are supplies to users so that less sulphur dioxide is produced when the fuel is burned.

Question 16

What are biofuels made from

Answer 16

Plant or animal products and are renewable

Question 17

What is biodiesel made from

Answer 17

Vegetable oils extracted from plants

Question 18

What are the advantages of biodiesel

Answer 18

It makes little contribution to carbon dioxide levels. This is because the carbon dioxide given off when it burns was taken from the atmosphere by the planet when it grew

Question 19

What are the disadvantages of using biodiesel

Answer 19

The plants that are grown for biodiesel use large areas of farmland

Question 20

What is an example of a biofuel

Answer 20

Ethanol made from sugar cane or sugar beet

Question 21

What are the advantages and disadvantages of using hydrogen as a fuel

Answer 21

Advantage:
-it produces only water when burned

Disadvantage:

• it’s a gas so it takes up a large volume. This makes it difficult to store
• requires large amounts of energy to be produced from water by electrolysis

Question 22

What are fractions

Answer 22

Liquids that boil within different temperature ranges