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Key Facts to Memorise

Part of Electrolysis of Aqueous Solutions · GCSE GCSE Chemistry revision

This key facts covers Key Facts to Memorise within Electrolysis of Aqueous Solutions for GCSE Chemistry. Revise Electrolysis of Aqueous Solutions in Electrolysis for GCSE Chemistry with 21 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 6 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 6 of 13

Practice

21 questions

Recall

15 flashcards

📌 Key Facts to Memorise

  • Aqueous solutions have 4 ions: 2 from the dissolved compound + H⁺ and OH⁻ from water
  • Cathode rule: Metal above H → hydrogen forms; Metal below H → metal forms
  • Anode rule: Halide present → halogen forms; No halide → oxygen forms
  • CuSO₄ solution products: Copper at cathode (Cu below H) + Oxygen at anode (sulfate not a halide)
  • NaCl solution products: Hydrogen at cathode (Na above H) + Chlorine at anode (chloride is a halide)
  • Half equation for H₂: 2H⁺ + 2e⁻ → H₂
  • Half equation for O₂: 4OH⁻ → O₂ + 2H₂O + 4e⁻
  • Gas tests: H₂ = squeaky pop with lighted splint; O₂ = relights glowing splint; Cl₂ = bleaches damp litmus paper white
  • Brine electrolysis makes H₂ + Cl₂ + NaOH (three valuable products!)

Quick Check: When copper sulfate solution (CuSO₄) is electrolysed, what forms at the cathode and why?

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.

Key DefinitionsHigher Tier: Half Equations for Aqueous ElectrolysisThe Water ComplicationElectrolysis of Brine — Click to Explore

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.

21 questions on Electrolysis of Aqueous Solutions — practise free

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Higher Tier: Half Equations for Aqueous Electrolysis