Common Misconceptions

⚠️ Common Misconceptions

Misconception 1: "Only the dissolved compound's ions are present in solution"

This is one of the most common errors. Water itself partially ionises: H₂O ⇌ H⁺ + OH⁻. So ANY aqueous solution always contains H⁺ and OH⁻ ions in addition to those from the dissolved salt. This is why the products of aqueous electrolysis can differ from molten electrolysis — hydrogen or oxygen may form instead of the metal or non-metal from the original compound.

Misconception 2: "The more concentrated the solution, the less likely the halogen forms"

The opposite is true. In a dilute halide solution, the OH⁻ concentration is relatively higher, so oxygen may form preferentially at the anode. In a CONCENTRATED halide solution (like brine), Cl⁻ ions greatly outnumber OH⁻ ions, so chlorine is produced. Concentration matters for the anode product when a halide is present.

Misconception 3: "Sodium metal forms at the cathode when brine is electrolysed"

Sodium does NOT form — hydrogen gas forms instead. Because sodium is above hydrogen in the reactivity series, H⁺ ions are more easily reduced and are preferentially discharged. To obtain sodium metal directly, you would need to electrolyse MOLTEN sodium chloride (no water present), as in the Downs process.