Explain why ionic compounds conduct electricity when molten or dissolved in water.
Describe reactions during electrolysis at positive and negative electrodes.
Identify reactions as reduction or oxidation (higher tier students).
Introduction to Electrolysis
Electrolysis can initially seem tricky but becomes clearer with understanding.
Video series will cover general ideas and specific examples.
Ionic Compounds Recap
Example: Lead Bromide (PbBr₂)
Formed from reaction of lead (Pb) with bromine (Br).
Lead atom loses 2 electrons to form Pb²⁺ ion.
Bromine atoms gain the electrons to form Br⁻ ions.
Electrolysis Key Facts
Solid Ionic Compounds:
Cannot conduct electricity.
Ions are locked in a regular pattern and held by strong electrostatic forces.
Molten/Dissolved Ionic Compounds:
Forces of attraction are broken; ions are free to move.
Liquids/solutions are known as electrolytes and can conduct electricity.
Electrolysis of Molten Lead Bromide
Components:
Lead Bromide contains:
Positive lead ions (Pb²⁺)
Negative bromide ions (Br⁻)
Electrodes:
Made of conducting material (graphite/metal).
Cathode (negative electrode): Attached to negative terminal of power supply, covered with electrons.
Anode (positive electrode): Connected to positive terminal of power supply, has a lack of electrons.
Process:
Positive lead ions attracted to cathode; gain 2 electrons to form lead atoms (reduction reaction).
Negative bromide ions attracted to anode; lose 1 electron to form bromine atoms (oxidation reaction).
Bromine atoms pair up to form bromine molecules.
Next Steps
Future video: Using electrolysis to extract reactive metals like aluminium.
Practice questions available in the revision workbook.
Review
You should now understand the principles of why ionic compounds conduct electricity when molten or dissolved, and the reactions at electrodes as reduction or oxidation.