Extraction of Metals

Question 1

How do we have to extract metals that are more reactive than carbon?

Answer 1

Using electrolysis of molten compounds

Question 2

Give an example of a metal that has to be extracted using electrolysis

Answer 2

Aluminium

Question 3

Name a disadvantage of using electrolysis compared to reduction using carbon?

Question 4

Describe how extracting aluminium is an expensive process

Answer 4

A high temperature is needed to melt aluminium oxide so that aluminium can be extracted - requiring a lot of energy

Question 5

Why do we use electrolysis with copper when we can extract it using reduction with carbon?

Answer 5

After extracting the copper through reduction with carbon it is still very impure

• electrolysis is used to purify it

Question 6

Describe how copper is purified using reduction with carbon, and name the process

Answer 6

Smelting

Copper ore is heated in a furnace

Question 7

What is the problem with impure copper?

Answer 7

It can’t conduct electricity very well, which is a problem as a lot of copper is used to make electrical wiring

Question 8

Why do we extract copper using reduction with carbon BEFORE we electrolyise it?

Answer 8

It’s less expensive than just using electrolysis

Question 9

Define ‘electrolysis’

Answer 9

Breaking down a substance using electricity

Question 10

What does electrolysis require?

Answer 10

A liquid to conduct the electricity, known as the electrolyte

Question 11

What 2 things are electrolytes usually made of?

Answer 11

1. Metal salt solutions made from the ore (e.g. copper sulphate
2. Molten metal oxides

Question 12

How can electrolytes conduct electricity?

Answer 12

Because they contain free ions

Question 13

Describe what the negative and positive electrodes do with the electrons

Answer 13

Negative electrode - gives away electrons

Positive electrode - takes away electrons

Question 14

As the ions lose or gain electrons, what happens to them?

Answer 14

They become atoms or molecules and are released

Question 15

Give the 4 steps of how electrolysis is used to get pure copper

Answer 15

1. Electrons are pulled off copper atoms at the positive electrode
2. This causes them to be released into the solution as Cu²⁺ ions
3. Cu²⁺ ions near the negative electrode gain electrons and turn back into copper atoms
4. The impurities are dropped at the positive electrode as sludge, whilst the pure copper atoms bond to the negative electrode

Question 16

Describe the negative electrode for the electrolysis of copper

Answer 16

Starts off as a thin piece of pure copper and more pure copper adds to it

Question 17

Describe the positive electrode for the electrolysis of copper

Answer 17

A lump of impure copper which will dissolve

Question 18

Why is the Statue of Liberty green?

Answer 18

Because the copper coating reacts with the oxygen in the air to form copper carbonate

Question 19

More reactive metals react ____ ____ than less reactive ones

Answer 19

More reactive metals react more vigorously than less reactive ones

Question 20

What happens if you put a reactive metal into a soltion of a dissolved metal compound?

Answer 20

The reactive metal will replace the less reactive metal in the compound

Question 21

Why do more reactive metals displace less reactive metals?

Answer 21

The more reactive metal bonds more strongly to the non-metal part of the compound and pushes out the less reactive metal

Question 22

Explain what happens when you add scrap iron to a solution of copper sulfate, and why this is useful

Answer 22

The more reactive iron displaces the copper, so you are left with copper metal and iron sulfate

This is useful because iron is cheap but copper is expensive

Question 23

What happens if a piece of silver is put into a copper sulfate solution?

Why?

Answer 23

Nothing

Because the copper is the more reactive metal, and it is already bonded to the sulfur

Question 24

Why is it important to recycle as much copper as possible?

Answer 24

Because the supply of copper-rich ores is limited

Question 25

The demand for copper is ____, and this may lead to ____ in the future

Answer 25

The demand for copper is growing, and this may lead to shortages in the future

Question 26

What is the demand and limited supply of copper causing scientists to do?

Answer 26

Look into new ways of extracting copper from low-grade ores, or from the waste that is currently produced when copper is extracted

Question 27

Name two examples of new methods to extract copper

Answer 27

1. Bioleaching
2. Phytomining

Question 28

Define ‘bioleaching’

Answer 28

Using bacteria to separate copper from copper sulfide.

Question 29

Describe the process of bioleaching

Answer 29

The bacteria get energy from the bond between copper and sulfur, serparating out the copper from the ore in the process. The leachate (the solution produced by the process) contains copper, which can be extracted

Question 30

Give an example of how the copper can be separated out from the leachate

Answer 30

Filtration

Question 31

Define ‘phytomining’

Answer 31

Growing plants in soil that contains copper, then harvesting them

Question 32

Describe the process of phytomining

(4 steps)

Answer 32

1. Plants are grown in soil that contains copper.
2. The plants can’t use or get rid of the copper so it gradually builds up in the leaves.
3. The plants can be harvested, dried, and burned in a furnace.
4. The copper can be collected from the ash left in the furnace.

Question 33

Name an advantage of bioleaching and phytomining to traditional methods of copper extraction

Answer 33

They have a much smaller impact on the environment

Question 34

Name a disadvantage of bioleaching and phytomining to traditional methods of copper extraction

Answer 34

They are much slower