This exam tips covers Exam Tips for Electrolysis of Aqueous Solutions 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 12 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.

💡 Exam Tips for Electrolysis of Aqueous Solutions

🎯 Common Question Types:

"Predict the products at each electrode when [solution] is electrolysed" (2-4 marks)
"Explain why hydrogen forms at the cathode rather than sodium" (2 marks)
"Give the test for chlorine gas" (1 mark)
"State three products of brine electrolysis and a use for each" (3 marks)

📝 Key Command Words:

Predict — apply the two rules and state the product with brief justification
Explain — give the reasoning (e.g., why H⁺ is preferentially discharged over Na⁺)
State — a simple factual answer required (e.g., gas test result)

⚠️ Common Mistakes to Avoid:

Forgetting that water contributes H⁺ and OH⁻ ions — these are always present
Saying sodium forms at the cathode when brine is electrolysed (it doesn't — hydrogen forms)
Confusing the oxygen half equation — it forms 2H₂O as a by-product: 4OH⁻ → O₂ + 2H₂O + 4e⁻
Not learning the gas tests — these are very easy marks!

Quick Check: Name the three products of brine electrolysis and give one use for each.

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.

Exam Tips for Electrolysis of Aqueous Solutions