To monitor the quantity of copper metal deposited during electrolysis of copper sulphate solution.

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                             Electrolysis of Copper Sulphate solution

Aim:

To monitor the quantity of copper metal deposited during electrolysis of copper sulphate solution.

Introduction:

When a solution of copper sulphate is electrolysed using carbon or platinum electrodes, copper is obtained at the cathode and oxygen at the anode. On the other hand when copper electrodes are used instead, something unusual happens.

At the cathode: Copper ions become atoms, as you would expect:

( Cu2+ ) + ( 2e- )  Cu

The copper atoms cling to the cathode.

At the anode: The copper anode dissolves, forming copper ions:

Cu  ( Cu2+ ) + ( 2e- )

So the anode wears away, while the cathode grows thicker. If you weigh them you will find that:

Mass of copper lost by anode = Mass of copper gained by cathode.

This electrolysis is used in industry to purify copper, which has to be very pure for use in electrical wires. The impure copper is made into an anode. As it wears away, the cathode gets plated with pure copper while impurities fall to the bottom of the electrolysis cell.

Faraday’s First Law Of  Electrolysis:

“The mass of any element deposited during electrolysis is directly proportional to the number of coulombs of electricity passed ”.

Faradays Second Law Of Electrolysis:

“The mass of an element deposited by one Faraday of electricity (96500 Coulombs) is equal to the atomic mass in grams of the element divided by the number of electrons required to discharge one ion of the element ”.

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Apparatus:

  1.            Power pack for supply electricity.

  1.            Ammeter for measuring current.

  1.            Variable resister to control flow of current keep constant at 0.2A.
  2.            Beaker to contain Copper Sulphate solution (Cu SO4.

  1.            Copper electrodes marked A for positive (+ve) electrode and C for negative (-ve) electrode.

  1.           Top pan balance for taking mass.
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