Overview
This lecture explains the process of electrolysis, focusing on using it to separate elements in insoluble ionic compounds like lead bromide, and covers the necessary equipment and chemical processes involved.
What is Electrolysis?
- Electrolysis means "splitting up with electricity" and is used to separate elements in ionic compounds.
- It requires passing an electric current through an electrolyte.
Equipment Needed for Electrolysis
- A beaker to hold the electrolyte (liquid or solution containing free-moving ions).
- Electrolytes can be aqueous solutions (e.g., copper sulfate in water) or molten ionic compounds (e.g., melted lead bromide).
- Two electrodes: anode (positive) and cathode (negative), typically made of metal or carbon.
- Wires to connect electrodes and a power supply (battery) to drive electron flow.
Electrolysis Process (Lead Bromide Example)
- Molten lead bromide contains free-moving lead ions (Pb²⁺) and bromide ions (Br⁻).
- Negative bromide ions (Br⁻) move to the positive anode, get oxidized, and form bromine gas (Br₂).
- Positive lead ions (Pb²⁺) move to the negative cathode, get reduced, and form pure molten lead.
- Electrons from bromide ions are transferred to the anode, then move through the external wire to the cathode, reducing lead ions.
Chemical Changes at Electrodes
- At the anode: Bromide ions are oxidized (lose electrons) to form bromine.
- At the cathode: Lead ions gain electrons (are reduced) to form pure lead.
- The overall process uses electricity to convert ions back into pure elements by transferring electrons.
Key Terms & Definitions
- Electrolyte — A liquid or solution containing free-moving ions that conducts electricity.
- Electrode — A solid conductor where electricity enters or leaves the electrolyte.
- Anode — The positive electrode where oxidation occurs.
- Cathode — The negative electrode where reduction occurs.
- Oxidation — Loss of electrons by an ion or atom.
- Reduction — Gain of electrons by an ion or atom.
- Half Equation — An equation showing either the oxidation or reduction process at an electrode.
Action Items / Next Steps
- Review how to label or draw the electrolysis apparatus.
- Prepare for upcoming lessons on the electrolysis of metal oxides and aqueous solutions.