3.6 Electrolysis 2 - Aluminium Oxide

Question 1

What is the cheap and easy way to extract metals from their ores?

Answer 1

Reduction with carbon - where the carbon atoms displace the metal in the metal oxide to form pure metal and carbon dioxide

Question 2

Why do we have to use electrolysis sometimes to extract metals from their ores?

Answer 2

If a metal is too reactive to be reduced with carbon or reacts with carbon, then electrolysis can be used to extract it

Question 3

What is one disadvantage of using electrolysis to extract metals from their ores?

Answer 3

Very expensive as lots of energy is required to melt the ore and produce the required current

Question 4

How do we make the solid Aluminium Oxide into molten Aluminium Oxide in order for it to be our electrolyte? (3)

Answer 4

1. Purify the aluminium oxide from the bauxite that we mined from the ground
2. Aluminium oxide has a melting point of over 2000 degrees so we first mix it with a mineral called cryolite. This lowers the melting point.
3. Aluminium oxide is heated to a very high temperature to form molten aluminium oxide.

Question 5

Are the aluminium or oxygen ions attracted to the positive anode electrode?

Answer 5

Oxygen ions

Question 6

Are the aluminium or oxygen ions attracted to the negative cathode electrode?

Answer 6

Aluminium ions

Question 7

What happens when the negatively charged Oxygen ions move to the positively charged anode?

Answer 7

They each lose two electrons and are discharged to neutral Oxygen atoms. The neutral oxygen atoms combine to form 02 molecules and float off into the air.

Question 8

What happens when the positively charged Aluminium ions move to the negatively charged cathode?

Answer 8

It will gain 3 electrons each to form Aluminium atoms which will slowly pool in the bottom of the beaker as molten Aluminium metal.

Question 9

Why does the anode in this experiment need to be changed regularly?

Answer 9

The electrode is made of carbon. The anode needs to be replaced regularly as it reacts with oxygen to produce carbon dioxide.

Question 10

At the anode, are the Oxygen ions being oxidised or reduced?

Answer 10

Oxidised

Question 11

At the cathode, are the Aluminium ions oxidised or reduced?

Answer 11

Reduced

Question 12

What does OILRIG stand for?

Answer 12

Oxidation
Is
Loss
Reduction
Is
Gain

Question 13

Which two chemical processes are used to extract metals from their ores?

Answer 13

• Electrolysis
• Reduction with carbon

Question 14

Why is electrolysis not used to extract all metals?

Answer 14

Electrolysis is expensive because it requires a large amount of electricity

Question 15

When should a metal be extracted by carbon reduction?

Answer 15

When the metal is less reactive than carbon

Question 16

What is the name of the substance that is mixed with aluminium oxide to lower its melting point?

Answer 16

Cryolite