Electrolysis: brine
Lesson details
Learning outcome
I can describe the reactions of electrolysis of an aqueous solution of sodium chloride, including the tests for identifying the products.
Key learning points
- There are four ions present in a solution of brine: H⁺, OH⁻, Na⁺ and Cl⁻.
- The product at the negative electrode is hydrogen gas.
- The product at the positive electrode is chlorine gas.
- Sodium hydroxide solution forms in the electrolyte solution, making it alkaline.
- Two types of ions are in competition at each electrode.
Keywords
Brine - A concentrated aqueous solution containing between 3.5% and 26% sodium chloride.
Anode - A positively charged electrode, in an electrolysis cell, to which the anions are attracted.
Cathode - A negatively charged electrode, in an electrolysis cell, to which the cations are attracted.
Reduction - Reduction is a type of reaction in which a substance loses oxygen or gains electrons.
Oxidation - Oxidation is a type of reaction in which a substance gains oxygen or loses electrons.
Common misconception
Pupils find it hard to remember what is formed at each electrode.
Remind pupils about the electrolysis rules and provide opportunities for them to apply the rules to different electrolytes. Use animations to show the ions present in brine and how they move in the electrolysis cell.
Teacher tip
Provide opportunities for pupils to carry out the electrolysis of brine for themselves.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which subatomic particle has a negative charge?
Q2.What is an electrolyte?
Q3.Which ion is discharged at the cathode during the electrolysis of aqueous solutions?
Q4.Which of the following definitions of oxidation are correct?
Q5.What determines whether hydrogen or a metal is produced at the anode during electrolysis?
Q6.What is produced at the anode during the electrolysis of an aqueous solution?
Assessment exit quiz
6 Questions
Q1.What ions are present in a solution of brine?
Q2.What is produced at the negative electrode during the electrolysis of brine?
Q3.What is the half-equation for the reaction at the anode during electrolysis of brine?
Q4.How can you test for hydrogen gas?
Q5.Why does the electrolyte become alkaline during the electrolysis of brine?
Q6.Which of the following statements describes what happens during the electrolysis of brine?
To help you plan your 11 chemistry lesson on: Electrolysis: brine, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 11 chemistry lesson on: Electrolysis: brine, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 chemistry lessons from the Electrolysis unit, dive into the full secondary chemistry curriculum, or learn more about lesson planning.