During electrolysis of a halide-containing solution, what is formed at the anode?

During electrolysis of a halide-containing solution, what is formed at the anode?

• A. Oxygen gas
• B. Hydrogen gas
• C. Halogen gas
• D. Metal ions

Answer: (C)

At the anode, oxidation occurs. In a halide-containing solution, the halide ions are readily oxidized to form the corresponding halogen gas. That is, two halide ions lose electrons to become a diatomic halogen molecule: 2X− → X2 + 2e− (for example, 2Cl− → Cl2 + 2e−). Water oxidation to oxygen gas can occur, but it is less favorable under typical conditions when halide ions are present in appreciable amounts, so halogen gas evolution dominates. This is why chlorine gas forms from chloride, bromine from bromide, and so on.

At the anode, oxidation occurs. In a halide-containing solution, the halide ions are readily oxidized to form the corresponding halogen gas. That is, two halide ions lose electrons to become a diatomic halogen molecule: 2X− → X2 + 2e− (for example, 2Cl− → Cl2 + 2e−). Water oxidation to oxygen gas can occur, but it is less favorable under typical conditions when halide ions are present in appreciable amounts, so halogen gas evolution dominates. This is why chlorine gas forms from chloride, bromine from bromide, and so on.