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Required Practical: Electrolysis of Aqueous Solutions

Part of Electrolysis of Aqueous Solutions — GCSE Chemistry

This required practical covers Required Practical: Electrolysis of Aqueous Solutions within Electrolysis of Aqueous Solutions for GCSE Chemistry. Revise Electrolysis of Aqueous Solutions in Electrolysis for GCSE Chemistry with 20 exam-style questions and 0 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 10 of 13 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.

Topic position

Section 10 of 13

Practice

20 questions

Recall

0 flashcards

🧪 Required Practical: Electrolysis of Aqueous Solutions

This is a named AQA required practical. Examiners ask you to describe the method, identify variables, and explain safety precautions — often for 4-6 marks.

Method

  1. Set up electrolysis apparatus with inert (carbon/graphite) electrodes in a beaker
  2. Pour the aqueous solution (e.g., copper sulfate, sodium chloride) into the beaker, ensuring both electrodes are submerged
  3. Connect the electrodes to a DC power supply using connecting wires and crocodile clips
  4. Switch on the power supply and observe what forms at each electrode for several minutes
  5. Test any gases produced: squeaky pop with a lighted splint for H₂; a glowing splint relights for O₂; damp litmus paper bleaches white for Cl₂
  6. Record observations and repeat with different aqueous solutions

Key Variables

  • Independent variable: Type of aqueous solution used (e.g., NaCl, CuSO₄, NaOH)
  • Dependent variable: Products formed at each electrode (identity and amount)
  • Control variables: Volume of solution, applied voltage, electrode material (inert carbon), time of electrolysis

Why Inert Electrodes?

Carbon/graphite electrodes are used because they do not react with the products or the electrolyte. If reactive metal electrodes were used (e.g., copper), the electrode itself would dissolve or react, changing the experiment — this is the principle behind electroplating (a different application).

Safety

  • Chlorine gas is toxic — if electrolyzing chloride solutions, work in a well-ventilated area or under a fume cupboard. Do not inhale the gas
  • Do not touch the electrodes when the power supply is switched on
  • Wear eye protection throughout
  • Copper sulfate solution is an irritant — avoid skin contact and wash hands after

Keep building this topic

Read this section alongside the surrounding pages in Electrolysis of Aqueous Solutions. That gives you the full topic sequence instead of a single isolated revision point.

Memory AidsExam FocusThe Water ComplicationElectrolysis of Brine

Practice Questions for Electrolysis of Aqueous Solutions

When sodium chloride (NaCl) is dissolved in water, which four types of ion are present in the solution?

  • A. Na⁺, Cl⁻, H⁺ and OH⁻
  • B. Na⁺, Cl⁻, H₂O and OH⁻
  • C. Na⁺, Cl⁻ only
  • D. Na⁺, Cl⁻, H₂ and O²⁻
1 markfoundation

Describe the three products formed when concentrated brine is electrolysed, and state where each is produced.

3 marksstandard

Quick Recall Flashcards

State the cathode rule for aqueous electrolysis.
If the metal is MORE reactive than hydrogen (above H in reactivity series) → hydrogen gas forms. If the metal is LESS reactive than hydrogen (below H) → the metal deposits. Examples: Na above H → H₂ forms. Cu below H → Cu deposits.
State the anode rule for aqueous electrolysis.
If a halide ion (Cl⁻, Br⁻, or I⁻) is present → the halogen gas forms. If NO halide is present → oxygen gas forms from the OH⁻ ions. Example: Cl⁻ present → Cl₂ forms. SO₄²⁻ present (no halide) → O₂ forms.

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