Edexcel IGCSEChemistryGeneral Applications7 Marks
Molten lead(II) bromide can be electrolysed using inert electrodes, as shown in Figure 2.
- (a)(i)Name the products formed at the positive electrode (anode) and the negative electrode (cathode).[2]
- (a)(ii)Write half-equations for the reactions occurring at the positive and negative electrodes.[2]
- (b)State the change that would be observed at the negative electrode during electrolysis.[1]
- (c)Explain why solid lead(II) bromide does not conduct electricity but molten lead(II) bromide does.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme. The mark or mark type is shown in brackets.
- For (a)(i):
- B1 for positive electrode: bromine (gas)
- B1 for negative electrode: lead (metal)
- For (a)(ii):
- M1 for 2Br⁻ → Br₂ + 2e⁻
- M1 for Pb²⁺ + 2e⁻ → Pb
- For (b):
- B1 for grey/silvery solid forms / molten lead forms
- For (c):
- M1 for (in solid state) ions are in fixed positions / cannot move
- M1 for (in molten state) ions are free to move / are mobile (and carry charge)
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