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Year 11
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Higher

Electrolysis: aqueous solutions practical

I can investigate what happens when aqueous solutions are electrolysed with inert electrodes.

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New
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Year 11
OCR
Higher

Electrolysis: aqueous solutions practical

I can investigate what happens when aqueous solutions are electrolysed with inert electrodes.

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Lesson details

Key learning points

  1. Electrolysis involves the decomposition / break-down of a substance by passing an electric current.
  2. Two types of positive ions are in competition at the negative electrode
  3. Two types of negative ions are in competition at the positive electrode
  4. There are rules for which substances are discharged at the anode and cathode
  5. The gases produced during electrolysis can be collected and tested

Keywords

  • Aqueous solution - formed when a substance is dissolved in water

  • Electrolyte - a liquid or aqueous salt solution that contains freely moving ions

  • Electrolysed - when a substance has been broken down by electrolysis

Common misconception

confusing the electrodes, electrical cables or carbon electrodes having a break in them

Use the PANIC acronym; positive anode negative is cathode. Check all components of the electric circuit.

Demonstrate the method to the class before they start the class practical.
Teacher tip

Equipment

electrolysis cell with graphite electrodes, power pack, electric leads with crocodile, test tubes, measuring cylinder, solutions of copper chloride, sodium chloride, copper sulfate, blue litmus paper

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
What is an electrolyte in the context of electrolysis?
A gas that facilitates electrical conduction.
Correct answer: A liquid or aqueous salt solution that contains freely moving ions.
A solid material that conducts electricity.
Q2.
What is formed when substances dissolve in water?
A gaseous mixture
Correct answer: An aqueous solution
A precipitate
Q3.
How does electrical conductivity in liquids occur?
Through the absorption of heat by the liquid.
Through the movement of electrons in the liquid.
Correct answer: Through the movement of ions in the liquid.
Q4.
Why are inert electrodes used in electrolysis?
To catalyse the electrolysis process.
To increase the conductivity of the solution.
Correct answer: To prevent the electrodes from reacting with the electrolyte.
Q5.
What happens to copper ions during the electrolysis of copper sulfate solution?
They are oxidised at the anode to form copper oxide.
Correct answer: They are reduced at the cathode to form copper metal.
They remain in solution.
Q6.
What are the products at the anode during the electrolysis of brine?
Correct answer: Chlorine gas
Hydrogen gas
Sodium metal

Exit quiz

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6 Questions

Q1.
What is the primary function of the cathode in electrolysis?
It attracts negative ions and facilitates their oxidation.
Correct answer: It attracts positive ions and facilitates their reduction.
It generates electric current.
It allows current to flow through it.
Q2.
What are the observations at the anode during the electrolysis of copper (II) chloride solution?
Correct answer: Bubbles of chlorine gas are produced.
Bubbles of oxygen gas are produced.
Copper metal is deposited.
Q3.
What happens at the cathode during the electrolysis of copper (II) sulfate solution?
Correct answer: Copper ions gain electrons and are reduced to copper metal.
Copper ions lose electrons and are oxidised to copper oxide.
Copper ions remain in solution and do not participate in the reaction.
Q4.
Explain why copper is deposited at the cathode during the electrolysis of copper (II) sulfate solution.
Correct answer: Copper ions gain electrons at the cathode and are reduced to copper metal.
Copper ions lose electrons at the cathode and are oxidised to copper oxide.
Copper ions remain in solution and do not participate in the reaction.
Q5.
During the electrolysis of brine, why is chlorine gas collected at the anode?
Correct answer: Chloride ions are discharged at the anode, releasing chlorine gas.
Hydroxide ions are discharged at the anode, releasing chlorine gas.
Sodium ions are discharged at the anode, releasing chlorine gas.
Q6.
What is the test for oxygen gas?
The gas turns limewater milky.
Correct answer: The gas relights a glowing splint.
The gas burns with a 'pop'.
The gas forms a white precipitate with acid.