4.4.3.4 - Electrolysis of aqueous solutions

What do the ions discharged when an aqueous solution is electrolysed using inert electrodes depend on?

The ions discharged when an aqueous solution is electrolysed using inert electrodes depend on the relative reactivity of the elements involved.

As well as ions from the ionic compounds, what other ions will be present in aqueous electrolyte solutions?

In aqueous solutions, as well as the ions from the ionic compound, there will be hydrogen and hydroxide ions (H+ and OH-) from the water

What is produced at the negative electrode?

At the cathode :

• Hydrogen gas is produced if the metal is more reactive than hydrogen.

• Otherwise a solid layer of the pure metal will be produced instead

What is produced at the positive electrode?

At the anode :

• oxygen is produced if the solution has no halide ions

• If the solution contains halide ions, then the halogen is produced

Why are halogens or oxygen produced at the anode?

As if OH- and halide ions are present, halogens are formed.

But if no halide ions are present, than the OH- ions are discharged and oxygen will be formed

Why does this happen?

As in aqueous solutions the water molecules break down producing hydrogen ions and hydroxide ions that are discharged.