the extraction of aluminum

Question 1

How reactive is aluminum?

Answer 1

It is less reactive than magnesium but more reactive than zinc or iron

Question 2

Why can carbon not be used in the extraction of aluminum?

Answer 2

Because it is not reactive enough

Question 3

What process is used to extract aluminum?

Answer 3

Electrolysis

Question 4

What is the compound electrolysed when extracting aluminum?

Answer 4

Aluminum oxide (Al2O3)

Question 5

What ore is aluminum extracted from?

Answer 5

Bauxite

Question 6

How is the ore for aluminum extraction mined?

Answer 6

By open cast mining

Question 7

What is the first step in the extraction of aluminum?

Answer 7

To separate the aluminum oxide from the ore, which contains a lot of rocky impurities such as iron(III) oxide

Question 8

What happens to the rusty brown waste solution?

Answer 8

It has to be stored in large lagoons

Question 9

Why is the aluminum oxide melted before it is electrolysed?

Answer 9

This enables the ions to move to the electrodes

Question 10

What is the disadvantage of having to melt the aluminum oxide?

Answer 10

It has a very high melting point of 2050ºC, which uses a lot of energy

Question 11

How can some of the energy by saved when melting this aluminum oxide?

Answer 11

By mixing it with molten cryolite

Question 12

What is cryolite?

Answer 12

Another ionic compound

Question 13

At what temperature can the new molten mixture be melted?

Answer 13

At about 850ºC

Question 14

What keeps the mixture molten?

Answer 14

The electrical energy transferred to the electrolysis cells

Question 15

What is the overall reaction in the electrolysis cell when extracting aluminum?

Answer 15

aluminum oxide, 2Al2O3 (l) –> aluminum, 4Al (l) + oxygen, 3O2(g)

Question 16

What are some uses of aluminium or its alloys?

Answer 16

• overhead power cables
• airplanes
• drink cans
• bicycle frames
• car bodies

Question 17

What happens at the cathodes in the electrolysis of aluminium oxide?

Answer 17

Each aluminium ion (Al^3+) gains 3 electrons, which turns the ions into aluminium atoms. Therefore the Al^3+ ions are said to have been reduced (as they gain electrons) or form Al atoms

Question 18

What is the half equation at the cathodes for the electrolysis of aluminium oxide?

Answer 18

Al^3+ (l) + 3e^- ––> Al (l)

Question 19

What happens to the aluminium metal formed?

Answer 19

It is molten at the temperature of the cell and collects at the bottom, where it is siphoned or tapped off

Question 20

What happens at the anodes in the electrolysis of alumium oxide?

Answer 20

Each oxide ion (O^2-) loses 2 electrons, which turns them into oxygen atoms. The O^2- ions are said to have been oxidised to form oxygen atoms, which bond in pairs to form molecules of oxygen gas (O2)

Question 21

What is the half equation at the anodes for the electrolysis of aluminium oxide?

Answer 21

2O^2- (l) ––> O2 (g) + 4e^-

Question 22

What happens to the oxygen formed at the anodes?

Answer 22

It reacts with the hot carbon anodes, making carbon dioxide gas

Question 23

What is the half equation for making carbon dioxide gas from the carbon anodes and oxygen gas formed?

Answer 23

C (s) + O2 (g) ––> CO2 (g)

Question 24

What happens to the carbon anodes?

Answer 24

They gradually burn away, and so they need to be replaced in the cells regularly