Electrolysis of molten lead(II) bromide

Steps:

• Molten PbBr₂ provides Pb²⁺ and Br⁻ ions for conduction.
• At cathode (negative electrode), Pb²⁺ ions gain electrons to form lead metal.
• At anode (positive electrode), Br⁻ ions lose electrons to form bromine gas.
• Bromine gas appears as a brown vapor at the anode.

Why A is correct:

• Anode reaction: 2Br⁻ → Br₂ + 2e⁻; bromine (Br₂) is a brown gas by definition.

Why the others are wrong:

• B: Electrons flow through the external circuit, not the solution.
• C: Ions migrate through the solution; the circuit carries electrons.
• D: Pb²⁺ ions are reduced at the cathode, not oxidized.

Final answer: A