1. Title: Electrolysis Complete the activities listed below
30/10/2019
Write a description of what you see happening in the animation. Use the keywords to help you. (Done? Sketch the diagram!)
Keywords: Positive, negative, electrode, ion, electrolyte, gain, lose

2. Title: Electrolysis Complete the activities listed below
30/10/2019
The electrolyte contains positive and negative ions.
Negative ions are attracted the positive electrode + lose electrons.
Positive ions are attracted to the negative electrode + gain electrons

3. What is electrolysis? Electro: from the word “Electricity”.
30/10/2019
Electro: from the word “Electricity”.
Lysis: from the Latin meaning “to split”/“to break”.
Electrolysis is the decomposition (breaking up) of a molten or dissolved ionic compound by electricity passed through it (Direct Current, DC).

4. Why molten or dissolved?
30/10/2019
As solids, ionic compounds form a lattice structure.
The ions (NOT ELECTRONS!!!) are held in place – cannot move.
Electrolysis requires a flow of electrical charge. The ions (NOT ELECTRONS!!!) NEED to be able to move to carry charge!
Molten (as liquid) the ions are free to move and carry charge.
Dissolved, the ions are free to move and carry charge.

5. Uses for electrolysis 30/10/2019
Particular compounds require electrolysis to be extracted from their ore and purified.
Metals that are more reactive than carbon (above carbon in the reactivity series) have to be extracted in this way as they cannot be displaced by carbon with heating.
Electrolysis is very expensive: it uses lots of electrical energy.

6. Extracting copper from Copper Chloride
30/10/2019
Which ion is going to the negative electrode? Why?
Which ion is going to the positive electrode? Why?
What products are being formed?

7. Extracting copper from Copper Chloride
30/10/2019
Copper ions (Cu2+); positive ions attracted to negative electrode.
Chloride ions (Cl-); negative ions attracted to positive electrode.
Negative electrode: copper atoms; Positive electrode: chlorine gas.

8. Half-equations: At the anode
30/10/2019
2Cl-  Cl2 + 2e-
Negative ions in the electrolyte lose electrons to the positive electrode.
This is “oxidation” – loss of electrons.
The negative ions lose their negative charge.
A neutral element forms.

9. Half-equations: At the anode
30/10/2019
Cu2+ + 2e-  Cu
Positive ions in the electrolyte gain electrons from the negative electrode.
This is “reduction” – gain of electrons.
The positive ions lose their positive charge.
A neutral element forms.

10. Have a go at balancing these half equations
30/10/2019
Cu2+ + 2e-  Cu
2Cl-  Cl2 + 2e-
Pb2+ + e-  Pb
Br-  Br2 + 2e-
H+ + e-  H2
Pb2+ + 2e-  Pb
2Br-  Br2 + 2e-
2H+ + 2e-  H2
Write half equations for the following ions:
Na+
Al3+
O2-
Na+ + e-  Na
Al3+ + 3e-  Al
2O2-  O2 + 4e-

11. Combining/Balancing Half Equations
30/10/2019
Combining/Balancing Half Equations
Na+ + e-  Na
2O2-  O2 + 4e-
Al3+ + 3e-  Al
Use the number of electrons to help balance the equations!
Na+ + e-  Na vs. 2O2-  O2 + 4e-
The number of electrons in each half equation must be equal!
We need to multiple Na+ + e-  Na by 4!
4Na+ + 4e-  4Na
Balance the half equations when combing:
2O2-  O2 + 4e- with Al3+ + 3e-  Al
Lowest common factor for electrons = 12
3x (2O2-  O2 + 4e- ) = 6O2-  3O2 + 12e-
4x (Al3+ + 3e-  Al) = 4Al e-  4Al

12. Electrolysis in Aqueous Solutions
30/10/2019
If in a solution during electrolysis there are two elements that can be produced at an electrode then the less reactive one will be the one that is formed e.g. consider the negative electrode (cathode):
Cu2+ ions and H+ ions: Cu forms
Ca2+ ions and H+ ions: H2 forms
Reactivity Series
1. Potassium
2. Sodium
3. Calcium
4. Magnesium
5. Aluminium
6. Zinc
7. Iron
8. Lead
9. Hydrogen
10. Copper
11. Mercury
12. Silver
13. Gold

13. Review
30/10/2019
Write a full explanation of what is happening in the animation below. Include: which ions go where, why they do this and both half equations.

14. Review
30/10/2019
The hydrogen ions are less reactive that the sodium ions.
The positive hydrogen ions are attracted to the negative electrode.
The hydrogen ions each gain one electron. 2H+ + 2e-  H2.
This is called reduction.
The negative chloride ions are attracted to the positive electrode.
Each chloride ion loses one electron. 2Cl-  Cl2 + 2e-
This is called oxidation.