Extraction of Metals.

Question 1

How are metals more reactive that carbon extracted?

Answer 1

Using electrolysis of molten compounds.

An example of a metal that has to be extracted in this way is aluminium.

Question 2

Why is electrolysis more expensive than reduction with carbon?

Answer 2

Because it uses alot more energy.

For example:

A high temperature is needed to melt aluminium oxide so that aluminium can be extracted- this requires a lot of energy, which makes it an expensive process.

Question 3

How is copper purified ?

Answer 3

By electrolysis.

1. Reduction of carbon The ore is heated in a furnace (this is called smelting)
2. Copper produced this way is impure- impure does not conduct electricity well. This isnt very useful becuase a lot of copper is used to make electrical wiring.
3. Electrolysis is also used to purify, eventhough it is expensive.
4. This produces very pure copper, which is a much better conductor.

Question 4

What is electrolysis?

Answer 4

The breaking down od a substance using electrictiy.

Question 5

What is the liquid to conduct the electricity for electrolysis called?

Answer 5

Electrolyte.

• often metal salt solutions (copper sulphate) or molten metal oxides.
• has free ions- these conduct the electricity and allow the whole thing to work.
• electrons are taken away by the positive electrode and given away by the negative electrode. As ions gain or lose electrons they become atoms or molecules and are released.

Question 6

How is electrolysis used to get copper?

Answer 6

1. Electrons are pulled off copper atoms at the positive electrode, causing them to go into solution Cu2+ ions.
2. Cu2+ ions near the negative electrode gain electrons and turn back into copper atoms.
3. The impurites are dropped at the positive electrode as a sludge, whilst pure copper atoms bond to the negative electrode.

Question 7

How do more reactive metals react, than less reactive metals?

Answer 7

They react more vigarously.

Question 8

What will happen if you put a reactive metal into a dissolved metal compound?

Answer 8

The reactive metal will replace the less reactive metal.

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

For example:

Scrap iron can be used to displace copper solution- useful because iron is cheap but copper is expensive. If some iron is put in the solution of copper sulphate, the more reactive one will ‘kick out’ the less reactive copper from the solution. You end up with iron sulphate and copper metal.

Copper sulphate + iron → iron sulphate + copper

If a piece of silver metal is put into the copper sulfate solution, nothing happens. The more reactive metal (copper) is already in the solution.

Question 9

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

Answer 9

Because the supply copper-rich ores are limited.

• The demand for copper is increasing and this may lead to shortages.
• Scientists: looking for new ways of extracting copper from low grade ores or from waste that is produced when copper is extracted.

Question 10

What are the two new ways of extracting copper?

Answer 10

Bioleaching:

Uses bacteria to seperate copper from copper sulfide. Bacteria gts energy from the bond between copper and sulfur, seperating out the copper from its ore. The leachate contains copper, which can be extracted by filtering.

Phytomining:

Involves growing plnts in soil that contain copper. Plant can’t use of get rid of copper so gradually builds up in leaves. Plants can be harvested, dried and burned in a furnace. Copper can be collected from ash left in furnce.

These have smaller impacts on the environment that traditional methods but is slower.