The Two Decision Rules — Learn These!
Part of Electrolysis of Aqueous Solutions — GCSE Chemistry
This diagram covers The Two Decision Rules — Learn These! 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 4 of 13 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.
Topic position
Section 4 of 13
Practice
20 questions
Recall
0 flashcards
🎯 The Two Decision Rules — Learn These!
⚡ CATHODE RULE — Check Reactivity Series!
Metal ABOVE hydrogen?
(K, Na, Li, Ca, Mg, Al)
→ HYDROGEN gas forms
2H⁺ + 2e⁻ → H₂
Metal BELOW hydrogen?
(Cu, Ag, Au, Pt)
→ METAL deposits
e.g., Cu²⁺ + 2e⁻ → Cu
⚡ ANODE RULE — Check for Halides!
Halide ion present?
(Cl⁻, Br⁻, I⁻)
→ HALOGEN gas forms
e.g., 2Cl⁻ → Cl₂ + 2e⁻
NO halide present?
(SO₄²⁻, NO₃⁻, etc.)
→ OXYGEN gas forms
4OH⁻ → O₂ + 2H₂O + 4e⁻