| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Chemistry |
| Lesson Topic: Predict the identity of the products at each electrode for the electrolysis of a halide compound in dilute or concentrated aqueous solution |
Learning Objective/s:
- Describe how reduction potentials and solution concentration influence electrode reactions during halide electrolysis.
- Predict the gases formed at the cathode and anode for both dilute and concentrated aqueous halide solutions.
- Apply a step‑by‑step decision process to identify the favoured half‑reaction in given scenarios.
- Analyse common misconceptions, such as why metal cations are not reduced in IGCSE electrolysis.
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Materials Needed:
- Projector and screen
- Whiteboard and markers
- Printed worksheet with half‑reaction tables and practice questions
- Diagram of an electrolytic cell (handout or slide)
- Safety goggles (if a live demonstration is shown)
- Power‑supply demo set (optional)
- Answer key for teacher
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Introduction:
Begin with a quick video of bubbling gases in an electrolytic cell to spark curiosity. Review the concepts of oxidation‑reduction, electrodes, and standard reduction potentials from the previous lesson. State that by the end of class students will be able to predict which gas appears at each electrode in both dilute and concentrated halide solutions.
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Lesson Structure:
- Do‑Now (5'): Students answer a short question on identifying cathode vs. anode on a diagram.
- Mini‑lecture (10'): Review half‑reactions, reduction potentials, and the effect of concentration (Nernst).
- Guided Practice (15'): Work through the 4‑step decision tree using a dilute NaCl example, checking understanding after each step.
- Worked Example (10'): Demonstrate predictions for concentrated NaCl, highlighting the switch to halogen evolution at the anode.
- Independent Practice (10'): Students complete two practice items (KBr dilute, CaCl₂ concentrated) on the worksheet.
- Check for Understanding (5'): Quick “exit ticket” where each pupil writes the cathode and anode products for a given concentration.
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Conclusion:
Summarise that water is always reduced at the cathode while the anode product depends on halide concentration. Collect exit tickets to gauge mastery and assign a short homework task: predict products for three new halide solutions and justify the reasoning.
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