The Extraction of Aluminium

Question 1

The three stage process of extraction of metals by electrolysis:

Answer 1

1. Mining the ore
2. Purification of the ore
3. Electrolysis of the ore

Question 2

The extraction of metal by electrolysis is _______.

Answer 2

Expensive

Question 3

What is the major ore of aluminium?

Answer 3

Bauxite

Question 4

What is the temperature to melt bauxite?

Answer 4

+2030 °C

Question 5

What is the catalyst of this process?

Answer 5

Cryolite, lower melting point to 900 - 1000 °C

Question 6

Only the ____ of aluminium gets rust.

Answer 6

Top

Question 7

Aluminium is a _____, _____ and _____ so it is used for cables but it’s ______ so only used for big important things.

Answer 7

• Good conductor
• Light
• Strong
• Expensive

Question 8

Why is aluminium expensive?

Answer 8

• Large amounts of energy are used in the extraction process
• Costly to replace anodes

Question 9

What is bauxite purified to produce?

Answer 9

Aluminium oxide (Al₂O₃)

Question 10

What can aluminium be extracted from?

Answer 10

Aluminium oxide (Al₂O₃)

Question 11

What method of extraction is used?

Answer 11

Electrolysis

Question 12

What is the name of the process?

Answer 12

Halt-Héroult Process

Question 13

What state must the aluminium oxide be in for electrolysis to work?

Answer 13

Molten

Question 14

Why must electrolysis be molten?

Answer 14

So that there are free electrons allowing an electrical current to pass through

Question 15

Why is it expensive to melt aluminium oxide?

Answer 15

It has a very high melting point, (+2030 °C).

Question 16

What do we do instead of melting aluminium oxide?

Answer 16

Dissolve it in molten cryolite

Question 17

Why do we use molten cryolite instead of aluminium oxide?

Answer 17

It reduces some of the energy costs involved in extraction, lower melting point

Question 18

What are both the anode and cathode made from in aluminium extraction electrolysis?

Answer 18

Graphite

Question 19

Where does aluminium metal form?

Answer 19

At the cathode and sinks to the bottom of the tank, where it is tapped off

Question 20

What forms at the anode?

Answer 20

Oxygen

Question 21

What else happens at the anode?

Answer 21

The oxygen reacts with the carbon of the anode and forms carbon dioxide

Question 22

Why do the anodes have to be frequently replaced?

Answer 22

The formation of carbon dioxide means that they gradually burn away

Question 23

Oxidation occurs at the _____.

Answer 23

Anode

Question 24

Reduction occurs at the _____.

Answer 24

Cathode

Question 25

What does the Halt-Héroult Process involve?

Answer 25

• Dissolving aluminium oxide (alumina) in molten cryolite

* Electrolysing the molten salt bath

Question 26

Half equation at anode.

Answer 26

2O⁻² → O₂ + 4e⁻

Question 27

Half equation at cathode.

Answer 27

Al³⁺ + 3e- → Al

Question 28

It is much _____ to _____ the metal.

Answer 28

• Cheaper

* Recycle