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Electrolysis Coursework

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Introduction

GCSE Chemistry - Electrolysis Coursework AIMS It is known that by passing a constant electric current through an aqueous copper sulphate solution that the passage of ions through this solution results in copper atoms being dissolved into the solution from the anode while positive copper ions (cations) being discharged at the cathode. Normally anions are discharged at the anode. The experiment carried out aimed to monitor the quantity of Copper (Cu) metal deposited during the electrolysis of Copper Sulphate solution (CuSo4) using Copper electrodes, when certain variables were changed. It was considered that the following factors could affect the deposition of Copper metal on the cathode. 1. Time 2. Current 3. Temperature 4. Molarity/Concentration of Solution 5. Quantity of Solution 6. Size of Electrodes 7. Distance between the electrodes 8. The surface of the electrodes The time was chosen because it is an easy quantity to measure and record, whilst at the same time maintaining the other variables at a constant level. The other factors could be observed in later experiments, should time allow. PREDICTIONS It is possible to predict that the relationship will be directly proportional between the time the current flows and the mass of Copper deposited on the Cathode (negative electrode). I can therefore predict that if I double the time of the experiment, I will therefore be doubling the charge. ...read more.

Middle

� Faradays = 300/96500 � Moles Copper = 0.0031088/2 � Mass = 0.0015544 x 64 � Mass = 0.0995 grams These equations will help to support my predictions, as from these equations a "theoretical" table of values can be produced and those can be plotted against the actual result's obtained. From this comparison, it will be possible to spot any anomalies in the results and from this explain why these may have occurred (see EVALUATION). METHOD The apparatus was set up as in the diagram below: Copper Sulphate solution (50cm3) was poured into a small beaker. The two copper electrodes were thoroughly cleaned using water and steel wool, to scratch off the layers of copper from previous experiments. The electrodes were weighed, their masses recorded and placed into the beaker containing Copper Sulphate solution. The electrodes were connected to a cell and ammeter. A steady current flowed (0.2 Amps) and the experiment was stopped at definite times (i.e. 5,10,15,20,25 minutes). At these times the current was switched off and both electrodes were removed from the solution. They were then washed by dipping in distilled water, and dried by dipping into propanone (a highly volatile liquid which readily evaporates) and placed near an electric heater. Once clean and dry both electrodes were both carefully weighed and their subsequent masses recorded. ...read more.

Conclusion

Cu EVALUATION Although this was a successful experiment, there were some factors of the experiment, which could have been improved to make it even more successful. One of these factors could have been the electrodes, which, even after a good clean were still quite dirty and obviously still had irremovable substances from previous experiments still attached to them. If this experiment were to be repeated for a second time, in need of greater accuracy, it would be imperative to have a new pair of electrodes, which have never been used before. Another factor which may have affected the overall outcome of the investigation, may have been the fact that the practical work of the investigation was carried over from lesson to lesson, meaning that variables such as the concentration or the amount of the Copper Sulphate solution could have changed between lessons. To overcome this problem, a stock solution of Copper Sulphate should have been made so as the concentration remained the same at all times. The same electrodes and equipment should have been used throughout. Also, when weighing, the same electrical balance should have been used as there may have been slight differences between the two balances. This is what could explain the anomaly ("freak" result) in the graph. I found this investigation very interesting and am looking forward to investigating more of the variables in this experiment, which may or may not affect the mass of copper deposited onto the cathode, such as changing the Current or Temperature variable. ...read more.

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