1. Title: Uses of Electrolysis Complete the activities listed below
22/11/2018
Title: Uses of Electrolysis Complete the activities listed below
Lesson aim: Know a range of uses of electrolysis and explain the reasons for them. Balance some more half equations!
Discuss:
How might be use electrolysis to:
Make jewellery cheaper?
Make objects more appealing?
Make objects more resistant to corrosion?

2. Uses of electrolysis: Electroplating
22/11/2018
Electroplating: applying a thin layer of metal to an object by electrolysis.
Why do this?
Improves appearance.
Improves resistance to corrosion (coating a reactive metal with a less reactive metal).
Reduces costs: Making jewellery (for example) out of cheaper metal (like Nickel) and plating it with gold/silver.

3. Uses of electrolysis: Aluminium Manufacture
22/11/2018
Aluminium is the most abundant metal in the Earth’s crust.
Most commonly found in an Ore called Bauxite:
Found in bauxite as aluminium hydroxide. Al(OH)3.
Can be converted into aluminium oxide, Al2O3.
Electrolysis is then required to extract the aluminium from its oxide:
Has to be electrolysis because aluminium is too reactive for other methods.
Electrolysis is expensive due to high energy requirements.
The aluminium oxide must be either liquid or dissolved.

4. Uses of electrolysis: Aluminium Manufacture
22/11/2018
Melting aluminium oxide requires LOTS of energy (aluminium’s melting point is 2054°C) - not ideal as it is very costly!
Charles Hall and Paul Héroult discovered:
Aluminium oxide will dissolve in molten cryolite.
Cryolite melts at 1012°C, less than half the temp. of Al2O3!
The electrolyte is therefore a mixture of aluminium oxide/cryolite:
The electrolyte is heated (to keep cryolite molten) by electricity.
This same electricity is used during the electrolysis process, using the electricity for 2 purposes.
Using fewer fossil fuels during the heating process means less carbon emissions (CO2) – less damage to the environment!

5. Uses of electrolysis: Aluminium Manufacture
22/11/2018
Negative electrode lines the electrolysis cell.
The positive electrodes dip into the electrolyte.
Carbon is used as both the positive and negative electrode.
200,000A of electrical current are passed through the electrolyte.
Balance these half equations:
Al3+ + __e-  Al
__O2-  O2 + __e- 3 2 4

6. Uses of electrolysis: The Chlor-Alkali Industry
22/11/2018
Uses of electrolysis: The Chlor-Alkali Industry
Involves the electrolysis of brine (Sodium chloride solution).
Used to make:
Chlorine gas (Cl2)
Hydrogen gas (H2)
Sodium hydroxide (NaOH) [sometimes called caustic soda].
Balance the following:
__H+ + __e-  H2
__Cl-  Cl2 + __e-
__NaCl(aq) + __H2O(l)  H2(g) + Cl2(g) + __NaOH(aq) 2 2 2 2 2 2 2

7. Complete the workbook Questions: Pg 91-93
22/11/2018
Complete the workbook Questions: Pg 91-93