Electrolysis of Molten Binary Compounds
Cambridge IGCSE Chemistry (0620) · 15 Questions · 27 Total Marks
📋 Exam Instructions
Answer all questions. For each question, attempt your own response before clicking Reveal Answer. Pay close attention to state symbols, half-equations, and exact Cambridge keywords required by the mark scheme.
Section A — Electrode Predictions
9 marksName the products formed at the cathode and anode during the electrolysis of molten potassium iodide, KI(l).
State the products formed at each electrode during the electrolysis of molten sodium chloride, NaCl(l).
Predict the products at each electrode during the electrolysis of molten magnesium chloride, MgCl₂(l).
During electrolysis, which electrode undergoes oxidation — the anode or the cathode? Explain using the movement of electrons.
Explain, in terms of ions, why a molten ionic compound can conduct electricity but the solid cannot.
Section B — Lead(II) Bromide Specifics
9 marksState TWO observations made at the anode during the electrolysis of molten lead(II) bromide, PbBr₂(l).
State TWO observations made at the cathode during the electrolysis of molten lead(II) bromide, PbBr₂(l).
Explain why the lead(II) bromide must be heated before electrolysis can occur.
Write the half-equation for the reaction at the cathode and state the type of reaction occurring at the cathode during the electrolysis of molten PbBr₂.
Write the half-equation for the reaction at the anode during electrolysis of molten PbBr₂ and identify the type of reaction occurring.
Section C — Apparatus & Safety
9 marksSuggest a suitable material for the electrodes used in the electrolysis of molten lead(II) bromide. Give a reason for your choice.
Explain why inert electrodes must be used in the electrolysis of molten lead(II) bromide.
[DRAWING] Draw and label a diagram of the apparatus used to electrolyse molten lead(II) bromide. Your diagram must show: the electrodes, the electrolyte, a power supply, and the direction of conventional current.
Reference Apparatus Diagram
State ONE safety precaution that must be taken during this experiment and explain why it is necessary.
Describe how you would test for the presence of bromine gas produced at the anode. State the positive result.
🏁 Key Electrolysis Rules to Memorise
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