To investigate the effect of the copper anode after electrolysing it in Copper Sulphate solution for certain periods of time

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ELECTROLYSIS OF COPPER

Aim: To investigate the effect of the copper anode after electrolysing it in Copper Sulphate solution for certain periods of time.

Planning:

Introduction: Electrolysis is the process of splitting up compounds or substances by passing an electric current through it. The substance being electrolysed is called an electrolyte. An electrolyte is a substance that cannot conduct when solid but can when molten or dissolved. In electrolysis, various equipment are involved in order to make the experiment successful. First of all, a power pack is needed. This acts as a pump to push electrons through the circuit i.e.) it provides energy. There are two electrodes involved. An electrode allows electrons to enter or leave a solution. It completes an electrical circuit. One electrode is called the Cathode, and one the Anode. The cathode is the negative electrode thus attracting the positive ions called cations. Electrons are drawn TOWARDS it. The anode on the other hand is the positive electrode thus attracting the negative ions called anions. Electrons are pulled AWAY from the anode.

Here is a diagram showing the set up of this experiment:

In this experiment there are several ions in solution. Copper 2+, Sulphate 2-, Hydrogen- and Hydroxide- ions. My electrodes will both be copper. Copper, being extremely low down in the reactivity series is discharged at the cathode before all ions except silver. So in this experiment copper will be discharged. Since the anode will be copper as well, both the copper in the solution and from the metal will be attracted towards the negatively charged cathode. "During this process, the impure anode loses mass because the copper atoms lose electrons and become copper ions.

Copper atoms copper ions + electrons

Cu (s) Cu 2+ + 2e-

The electrons released at the anode travel around the external circuit to the cathode. There the electrons are passed onto the copper ions from the CuSo4 solution and the copper is deposited on the cathode.

Copper ions + electrons Copper atoms

Cu 2+ + 2e- Cu (s)"

(GCSE Chemistry: B. Earl & L.D.R. Wilford)

Factors that affect the experiment:

Theory says that the mass lost at the anode is the mass gained at the cathode. I have proved this theory in my preliminary experiments.

The amount of time that the electrodes remain in the solution while being electrolysed makes a significant difference to the mass lost at the anode and the mass gained at the cathode. The current also affects the mass lost at the anode. Increasing the current increases the amount of electrons passing through the circuit. Voltage is directly proportional to current. You may either keep the current constant and vary the time or you could vary the time and keep the current stable. The concentration of the copper sulphate solution also affects the experiment. A few other things that affect the experiment other than the ones I've mentioned are:
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* The volume of a solution

* Distance between the electrodes

* Mass of electrodes

Prediction:

I predict that the longer amount of time that the anode stays in solution the more mass it will lose.

Fair Test:

In order to make this experiment a fair test, there are various factors that need to be kept constant as accurately as possible. The current that I will be using is going to be 1.5A. This current is allowed to drop or rise by 0.1A this way you can make sure that your results ...

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