experiment gf24d29202 1280 Electrolysis Of Copper(II) Sulphate Solution And Its Uses

Electrolysis Of Copper(II) Sulphate Solution And Its Uses


Crystals of copper(II) sulphate are white when dry and blue when hydrated. Copper(II) sulphate is a soluble ionic compound that is a good electrolyte. The products of the electrolysis of copper(II) depend on the nature of the anode.

Copper(II) sulphate solution dissociates as follows:

CuSO4(aq) โ†’ Cu2+(aq) + SO42-(aq)

H2O(l) โ‡Œ H+(aq) + OHโ€“(aq)

Electrolysis of copper(II) sulphate solution using copper electrodes

In copper(II) sulphate solution the ions present are Cu2+, SO42-, H+ and OHโ€“.

At the cathode

Cu2+ and H+ ions move to the cathode. Cu2+ ions are lower on the electrochemical series so they are preferentially discharged. Each Cu2+ ion gains two electrons to form a copper atom. The discharged copper atoms coat the cathode.

The cathode reaction is as follows:

Cu2+(aq) + 2e โ†’ Cu(s)


At the anode

OHโ€“ and SO42- move to the anode, but none of them is discharged. Instead, the copper atoms in the anode lose electrons and dissolve in the electrolyte to form copper ions, Cu2+. This process is known as electrode ionisation.

The anode reaction is as follows:

Cu โ€“ 2e โ†’ Cu2+(aq)

Overall result

The anode loses copper atoms and becomes thinner whilst the cathode gains an equal amount of copper atoms and becomes thicker. The concentration of copper(II) sulphate in the solution does not change and the solution remains blue.

Electrolysis of copper(II) sulphate solution using inert electrodes

In copper(II) sulphate solution the ions present are Cu2+, SO42-, H+ and OHโ€“.

At the cathode

Cu2+ and H+ ions move to the cathode. Cu2+ ions are lower on the electrochemical series so they are preferentially discharged. Each Cu2+ ion gains two electrons to form a copper atom. The discharged copper atoms coat the cathode.

The cathode reaction is as follows:

Cu2+(aq) + 2e โ†’ Cu(s)


At the anode

OHโ€“ and SO42- move to the anode and OHโ€“ are preferentially discharge because they are lower on the order of preferential discharge.

The anode reaction is as follows:

4OHโ€“(aq) โ€“ 4e โ†’ 2H2O(l) + O2(g)

As the area around the anode loses OHโ€“ ions, more water ionises creating an excess of H+ ions.

Overall result

Copper is deposited at the cathode and the cathode becomes thicker. Oxygen gas is released at the anode. The solution becomes acidic as the H+ and SO42- left in solution form sulphuric acid, H2SO4. The electrolyte becomes pale.

Uses of electrolysis of copper(II) sulphate solution in industry

1. Extraction of copper

Electrolysis is used to extract copper from large boulders of impure copper. An electrolytic cell is built around the boulder and copper(II) sulphate solution is added as electrolyte to the cell. The boulder is connected as the anode and a strip of pure copper is used as the cathode. An electric current is passed through and the copper is transfered from the boulder to the pure copper cathode. The impurities fall off.


2. Purification of copper

The last stage in the extraction of copper involves the purification of the impure copper produced. Impure copper is made the anode and pure copper is made the cathode in the electrolysis process. The copper is transfered form the anode to the cathode during the process. Impurities fall off.

3. Copper plating

Copper is shiny and resistant to corrosion. Reactive metals such as iron are coated with copper for decorative purposes and to prevent corrosion. The object to be plated is cleaned and connected as the cathode in any electrolytic cell containing copper(II) sulphate solution electrolyte. Pure copper is made the anode. During electroplating, the copper anode loses atoms and the object on the cathode gets coated with copper.