Electrolysis

L.O:

To be able to describe the uses and predict the products of electrolysis

Fuel cells

In a space rocket. Fuel cells react hydrogen with oxygen:

2H2 + O2 2H2O this makes electricity and drinking water

Water is electrolysed to make oxygen:

2H2O 2H2 + O2

Electrolysis of Water

2H2O 2H2 + O2

Hydrogen used as a fuel

Oxygen made used in nuclear submarines and spacecraft.

What is formed at the cathode and anode?

What are the half equations

Half Equations for Water

Anode :

4OH- ------------ O2 + 2H2O + 4e-

Cathode:

2H+ + 2e- ------- H2

Laptops

In groups of 3 or 4 you need to research how aluminium extracted from bauxite is made by electrolysis. You need to be able to explain what happens during the electrolysis and what the products are.

You have 30 mins!

Include a diagram, half equations and an explanation

Electrolysis of aluminiumAluminium is a reactive metal that is found in the ore bauxite combined with oxygen as aluminium oxide (Al2O3). Electrolysis breaks down the Al2O3 into aluminium and oxygen. As the aluminium loses oxygen, reduction takes place.

What is the word equation for the extraction of aluminium?

aluminium oxide aluminium oxygen +

Aluminium ore (bauxite) has a very high melting point (2,050°C). In electrolysis, the ore is dissolved in a compound called cryolite (Na3AlF6), which effectively lowers the melting point to 1,000 °C.

Aluminium from bauxite

Redox equations – aluminiumWhat processes occur at the electrodes during the electrolysis of aluminium oxide (Al2O3)?

What is the overall equation for this extraction by electrolysis?

At the negative electrode:

Al3+ + 3e- Al (reduction)

At the positive electrode:

2O2- O2 + 4e- (oxidation)

aluminium oxide aluminium + oxygen 2 Al2O3 (l) 4 Al (l) + 3 O2 (g)

Extracting aluminium summary