Reactivity and displacement reactions (extracting metals)

Question 1

What’s oxidation?

Answer 1

The reaction with/addition of oxygen

Question 2

What’s reduction?

Answer 2

Removal of oxygen

Question 3

How can you compare the reactivity of metals?

Answer 3

Using displacement reactions

Question 4

What’s a redox reaction?

Answer 4

Where oxidation and reduction occur simultaneously (REDuctionOXidation)

Question 5

What type of reaction is a displacement reaction?

Answer 5

Redox

Question 6

What happens during a displacement reaction?

Answer 6

The more reactive element reacts to take the place of a less reactive element in a compound

Question 7

What happens during a metal displacement reaction?

Answer 7

More reactive metal loses electrons (oxidises) and the less reactive metal gains electrons (reduces)

Question 8

What’s an ore?

Answer 8

An ore is a rock which contains enough metal to make extracting the metal from it economically worth while

Question 9

How can some metals less reactive than carbon be extracted from their ores?

Answer 9

Chemically by reduction using carbon, or silver and gold are found as uncombined elements
- When heated with carbon, if the metal is less reactive than carbon, carbon will displace the metal

Question 10

How can you extract metals more reactive than carbon?

Answer 10

Electrolysis (expensive)

Question 11

What are 2 biological methods to extract metals?

Answer 11

Phytoextraction
Bioleaching

Question 12

How does Bioleaching work?

Answer 12

• Uses bacteria to separate metals from their ores
• The bacteria get energy from the bonds between the atoms in the ore, separating out the metal from the ore
• The solution produced by the process is called the Leachate containing metal ions which can be extracted through electrolysis or displacement

Question 13

How does Phytoextraction work?

Answer 13

• Involves growing plants in soil that contains metal compounds
• The plant can’t get rid of or use the metals so they gradually build up in the leaves
• the plants can then be harvested, dried and burned in a furnace, the ash produced contains metal compounds from which the metal can be extracted by electrolysis or displacement

Question 14

What are the advantages and disadvantages of Biological methods of extraction?

Answer 14

Advantages - no harmful gases (e.g. sulphur dioxide) are produced and they cause less damage to the landscape than mining
Disadvantage - very slow

Question 15

Which is more expensive: electrolysis or reduction with carbon?

Answer 15

Electrolysis is expensive - it requires large amounts of electricity, and costs associated with melting or dissolving the metal ore so that it can conduct electricity
Reduction with carbon is cheaper - Carbon is cheap and already acts as a fuel to provide heat required for reduction to occur
So, metals lower down the reactivity series are cheaper to extract

Question 16

When does corrosion occur?

Answer 16

When a metal reacts with oxygen, making the metal weaker over time.
The metal becomes oxidised

Question 17

What happens during rusting?

Answer 17

The corrosion of iron requires water as well as oxygen (REDOX) and is called rusting

Question 18

What’s meant by ‘recycling metals’

Answer 18

Metals can be melted down and made into something new

Question 19

What are the pros of recycling?

Answer 19

• Protects environment: extracting metals is damaging to the environment, the mines destroy habitats —> recycling means that we don’t need as many mines, less waste in landfill sites
• Economic benefits: recycling saves money (because extraction required a lot of energy), recycling creates job opportunities

Question 20

What are the cons of recycling metals?

Answer 20

Could cost more to transport/sort metals

Question 21

What’s the purpose of life cycle assessments?

Answer 21

A life cycle assessment (LCA) can be carried out to work out the environmental impact of a product. The LCA also helps people to decide whether it is worthwhile to manufacture and recycle a product.

Question 22

What are the stages considered for the life cycle assessment of a product?

Answer 22

Obtaining materials
Manufacturing
Use of product
Disposal of product