Overview
This lecture explains electrolysis, focusing on how it separates elements in ionic compounds like lead bromide, including equipment, processes, and key reactions.
What is Electrolysis?
- Electrolysis is the splitting of a substance using electricity.
- It is used to separate elements from ionic compounds.
Equipment Needed for Electrolysis
- A beaker holds the electrolyte (liquid containing free-moving ions).
- Electrolyte must be able to conduct electricity; it can be a dissolved solution (aqueous) or molten (melted) ionic compound.
- Electrodes (usually metal or carbon) are inserted into the electrolyte.
- The positive electrode is called the anode; the negative electrode is the cathode.
- Electrodes are connected by wires and a power supply (e.g., battery).
Example: Electrolysis of Lead Bromide
- Molten lead bromide is used as the electrolyte, containing free lead ions (Pb²⁺) and bromide ions (Br⁻).
- Bromide ions (Br⁻) move to the anode, lose electrons (oxidation), and form bromine gas (Br₂).
- Lead ions (Pb²⁺) move to the cathode, gain electrons (reduction), and form pure lead (Pb).
Reactions at the Electrodes
- Oxidation occurs at the anode: Br⁻ → Br₂ + electrons.
- Reduction occurs at the cathode: Pb²⁺ + 2e⁻ → Pb.
- Electrons flow from the anode to the cathode via the external circuit (wire and battery).
Key Terms & Definitions
- Electrolyte — A liquid or solution with free-moving ions that conducts electricity.
- Anode — The positive electrode where oxidation happens.
- Cathode — The negative electrode where reduction happens.
- Oxidation — Loss of electrons.
- Reduction — Gain of electrons.
Action Items / Next Steps
- Be able to label and draw the electrolysis apparatus.
- Review the half-equations for oxidation and reduction.
- Prepare for upcoming lessons on metal oxide electrolysis and electrolysis of aqueous solutions.