When is electrolysis used

Instead, water molecules undergo reduction to liberate dihydrogen gas, H 2. For example, when a moderately concentrated aqueous solution of KCl is subjected to electrolysis using inert electrodes, only Cl - ions get discharged at the anode. Instead, water molecules undergo reduction to give dihydrogen H 2 gas.

However, the ions of less reactive transition metal series can be discharged in the aqueous medium. For example, the electrolysis of aqueous CuCl 2 , copper is deposited at the cathode along with the liberation of chlorine gas at the anode.

Some stable oxo anions like sulfate, phosphate, carbonate, nitrate, etc. Alternatively, the water molecules undergo oxidation at anode and thus by liberating dioxygen gas, O 2. But the nitrate ion, NO 3 - cannot be oxidized at the anode. In place of it, the water molecule is oxidized to liberate dioxygen gas, O 2 at anode. Regardless of the nature of the ions, only water molecules undergo electrolysis when dilute solutions are used.

For example, when a very dilute aqueous solution of NaCl is subjected to electrolysis, dihydrogen and dioxygen gases are liberated at cathode and anode respectively. In this case, NaCl helps in improving the electrical conductivity of water, which was otherwise a poor conductor. The electrodes become active when the metal used in one or either of them and the cation in the electrolyte belong to the same element.

The electrodes now enter into the electrolytic reaction. At anode, the metal undergoes oxidation and dissolves in the electrolyte, while the metal is deposited on cathode due to reduction of metal ions. For example, when an aqueous solution of silver nitrate, AgNO 3 is electrolyzed using silver electrodes, some amount of silver in the anode is dissolved into the solution and the same amount of silver is deposited on cathode. The subject that deals with electrolytic processes in metallurgy is generally referred to as electrometallurgy.

Electrolysis examples: Metals like sodium, potassium, aluminium, zinc etc. For strongly electropositive metals, molten electrolyte is subjected to electrolysis and for other less electropositive metals, aqueous solutions can be electrolysed.

The metals can be refined by electrolysis process generally referred to as electrorefining. In general, the metals are deposited at cathode. An impure sample of metal solution is electrolysed using cathode made up of same metal in pure state so that the metal from solution is deposited on it during electrolysis. The electroplating is used to improve corrosion resistance and in the making of ornaments. Processes involving electrolysis include: electro-refining , electro-synthesis , and the chloro-alkali process.

Example: When we electrolyze water by passing an electric current through it, we can separate it into hydrogen and oxygen. More information : The Electrolysis of Water.

For electrolysis to work, the compound must contain ions. Covalent compounds cannot act as electrolytes because they contain neutral atoms. The ions must be free to move, which is possible when an ionic substance is dissolved in water or it is melted. For example, if electricity is passed through molten lead bromide, the lead bromide is broken down to form lead and bromine.

This is what happens during electrolysis:. To be an electrolyte, a substance must be able to conduct electricity.