C1 - Extracting Metals

Question 1

Which type of compounds are usually found as ores?

Answer 1

Oxides

E.g. Aluminium oxide

Question 2

What are the 2 main ways of extracting metals from ores?

Answer 2

Reduction

Electrolysis

Question 3

How are metals purified?

Answer 3

Using electrolysis

Question 4

What is reduction with carbon?

Answer 4

When carbon reacts with the metal oxide to form the metal and carbon dioxide

Question 5

How can we work out if a metal can be extracted using reduction with carbon and why?

Answer 5

If the metal is below carbon in the reactivity series it can be reduced with carbon

This is because the carbon is more reactive so it will bond with the oxygen faster than the metal

Question 6

What do we do to cause reduction with carbon?

Answer 6

Heat the metal oxide (and carbon) in a blast furnace

Question 7

How are metals more reactive than carbon extracted?

Answer 7

Using electrolysis of molten compounds

Question 8

Why is electrolysis to extract aluminium so expensive?

Answer 8

The aluminium oxide has to be melted at a very high temperature

Question 9

Why is electrolysis used on copper?

Answer 9

Copper has to be purified so that it can be used in wires

Question 10

What is electrolysis?

Answer 10

The breaking down of a substances using electricity

Question 11

What is the electrolyte?

Answer 11

The liquid (can be molten or solution) that is to be broken down and conducts electricity

Question 12

What does an electrolyte have to have?

Answer 12

Free ions

Question 13

How does electrolysis work?

Answer 13

The positive ions go towards the negative electrode where they lose electrons and become the pure atoms

The negative ions gain electrons at the positive electrode and become the pure atoms

Question 14

How do we lower the melting point of the aluminium oxide in electrolysis?

Answer 14

Cryolite is added

Question 15

Why do we try to use reduction with carbon instead of electrolysis?

Answer 15

Electrolysis is much more expensive because the metal oxides have to be molten and the electricity is expensive

Question 16

What is the other way that copper can be extracted?

Answer 16

A displacement reaction with iron

Question 17

What is a displacement reaction?

Answer 17

AB + C (more reactive than A) –> CB + A

Question 18

Describe the displacement reaction used to extract copper

Answer 18

Copper sulfate + iron –> iron sulfate + copper

This is because iron is more reactibe than copper

Question 19

What are the 2 reasons iron is used to extract copper?

Answer 19

It is more more reactive than copper

It is cheaper than copper

Question 20

What is an ore?

Answer 20

A rock which contains enough metal to make it worthwhile extracting it

Question 20

Why do we need to recycle as much copper as possible?

Answer 20

Copper-rich ores are short in supply

Question 21

What is the other way of extracting metals?

Answer 21

Thermal decomposition

Question 22

What is the chemical equation for extracting metals using thermal decomposition?

Answer 22

Metal oxide –> mercury + oxygen (gas)

Question 23

Which metals can be extracted using thermal decomposition?

Answer 23

Mercury and silver

Question 24

Which metals are found as the element (native)?

Answer 24

Gold and platinum

Question 25

What are the 2 new methods of extracting copper?

Answer 25

Phytomining Bioleaching

Question 26

Describe bioleaching of copper

Answer 26

Bacteria separate copper from copper sulfide by getting the energy from the bond between the copper and sulfur The leachate (solution produced) is filtered to extract the copper

Question 27

Describe phytomining of copper

Answer 27

Plants are grown in copper-rich soil and the copper builds up in the leaves The plants are burned in a furnace and the ash has copper in and is collected

Question 28

What is the advantage and disadvantage of bioleaching and phytomining?

Answer 28

New methods of extraction don't destroy the environment but they are very slow

Question 29

What are the 2 advantages of metal extraction

Answer 29

Useful products made Provides money and jobs to local people

Question 30

What are the 2 disadvantages of metal extraction?

Answer 30

Bad for the environment (mines, noise, loss of habitats) Deep mine shafts are dangerous

Question 31

What are the 4 reasons for recycling metals?

Answer 31

Lots of energy used, fossil fuels burned Lots of energy used, recycling saves money Finite amount of metals in Earth, recycling saves them Cuts down metals sent to landfill

Question 32

Which metals don't have to be extracted from rocks and why?

Answer 32

Unreactive metals don't usually form compounds so they can be found as the metal itself

Question 33

What are the anode and cathode?

Answer 33

Anode is positive electrode Cathode is negative

Question 34

What are the anode and cathode made from?

Answer 34

They are both carbon (graphite)

Question 35

Why do anodes have to be replaced?

Answer 35

The oxygen reacts with the carbon anode to form carbon dioxide

Question 36

What is the other way that iron can be extracted in a blast furnace?

Answer 36

Iron oxide + carbon monoxide --> iron + carbon dioxide

Question 37

How is the carbon monoxide for this reaction obtained?

Answer 37

Coke (containing carbon) burns on air to produce heat and reacts to form carbon monoxide

Question 38

Describe how limestone is used in the blast furnace

Answer 38

The calcium carbonate reacts with the acidic impurities in the iron by reacting with them to form molten slag