In the same cell for molten lead(II) bromide, a coloured vapour is seen forming at electrode Y. Using inert electrodes, what is this product and at which el...
Question 1 Report
In the same cell for molten lead(II) bromide, a coloured vapour is seen forming at electrode Y. Using inert electrodes, what is this product and at which electrode is it released?
Answer Details
Electrode Y carries the + sign in the diagram, so Y is the anode. Negative ions are attracted to the positive electrode, and in molten lead(II) bromide the only negative ion is Br−.
At the anode the bromide ions lose electrons (oxidation):
2Br− → Br2 + 2e−
Bromine is a red-brown liquid that vaporises readily, so the coloured vapour at Y is brown bromine vapour, which matches the observation described.
Lead is the cathode product at X, not Y, because Pb2+ is positive and moves to the negative electrode. Oxygen and hydrogen cannot form because the compound is molten with no water present, so the only ions available are Pb2+ and Br−.
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