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Electrochemistry | IGCSE Chemistry (0620)

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CS-991 · Module I-4

4 · Electrochemistry

Cambridge IGCSE Chemistry 0620 · Core + Supplement · 2026–2028
Quick Revision
⚡ Electrolysis 🔌 Cathode / Anode 🧄 Electroplating

4.1 Electrolysis Basics

Electrolysis is the breakdown of an ionic compound, when molten or dissolved, by passing an electric current through it. Ions must be free to move — this only happens when molten or in aqueous solution, not in the solid state.

  • Cathode (negative electrode): attracts positive ions (cations), which gain electrons — reduction.
  • Anode (positive electrode): attracts negative ions (anions), which lose electrons — oxidation.
ElectrolyteCathode ProductAnode Product
Molten lead(II) bromideLead (metal)Bromine
Dilute sulfuric acid (aq)Hydrogen gasOxygen gas
Concentrated NaCl (aq, brine)Hydrogen gasChlorine gas
🎥 Video lectures for this sub-topic — coming soon
Q1: During electrolysis, reduction occurs at the:
a) Anode b) Cathode c) Both electrodes equally d) Neither electrode
Show Answer
✅ b) Cathode
Q2: Electrolysis of molten lead(II) bromide produces bromine at the:
a) Cathode b) Anode c) In solution d) It is not produced
Show Answer
✅ b) Anode
Q3: For electrolysis to occur, ions in a solid ionic compound must:
a) Stay fixed in place b) Be free to move (molten or dissolved) c) Be covalently bonded d) Be removed entirely
Show Answer
✅ b) Be free to move (molten or dissolved)

4.2 Electroplating

Electroplating uses electrolysis to coat one metal with a thin layer of another — for example, coating steel cutlery with silver, or copper with chromium for a decorative, corrosion-resistant finish.

  • The object to be plated is made the cathode (so the plating metal ions are attracted to it and deposit as a solid layer).
  • The plating metal itself is used as the anode (it dissolves into solution, continuously replenishing the ions used up).
  • The electrolyte is a solution containing ions of the plating metal.
🎥 Video lectures for this sub-topic — coming soon
Q1: In electroplating an object with silver, the object being plated is made the:
a) Anode b) Cathode c) Electrolyte d) Neither electrode
Show Answer
✅ b) Cathode
Q2: In electroplating, the metal used as the anode:
a) Stays solid and unchanged b) Dissolves into solution, replenishing ions c) Is not needed d) Becomes the electrolyte
Show Answer
✅ b) Dissolves into solution, replenishing ions
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