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The Electrolysis Of Copper Sulphate Solution Using Copper Electrodes

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Introduction

The Electrolysis Of Copper Sulphate Solution Using Copper Electrodes Plan Variables * Temperature of the electrolyte * The concentration of the electrolyte * The separation of he electrodes * The size of the electrodes * Current Only the mass or size of the electrodes, and the current are being investigated, therefore in order for this to be a fair test, the other factors must be kept constant. The temperature was monitored during the preliminary results, and the higher the current the higher the temperature change, which in the 1A reading was 5� C, therefore to keep it as constant as possible the current will be as low as possible, and monitored, so that it does not change during the experiment There will be a thermometer in the electrolyte so that the temperature can be monitored. The same CuS04 will be used throughout so the concentration is the same, and the same spacing between electrodes will be used. The size of the electrodes should be the same, but they will be reused, so the size will change from experiment to experiment. 1. Scrub copper electrodes with wire wool 2. Rinse in distilled water 3. Dry with propanone 4. Weigh and record anode and cathode 5. Put into circuit ate set current value, with crocodile clips, making sure the clips are not touching the copper sulphate. 6. Time for ten minutes 7. remove and dry, weigh and record result Evaluation There were several sources of error in this experiment as none of the results were 100% accurate. These error could have been caused by the fact that not all the ions "stick" to the anode, and so end up at the bottom of the solution. This happens most at higher levels of current, and causes the mass lost at the cathode to be greater than the mass gained at the anode. Also the temperature of the solution raised at higher currents by 5� C This would cause less ions to turn to copper at the anode, and make the current more, as there is less resistance. ...read more.

Middle

upon the charge passed through the cell. Now the charge passed, q (in Coulombs), is related to the current. I )in amps) and time, t (in seconds), by Faraday's law: q=ixt therefore I will predict that the mass change of the copper electrodes is directly proportional to the current and the time. Abstract This investigation looks at the factors which affect the rate mass of copper deposited at the cathode during the electrolysis of Cupric Sulphate solution using Copper electrodes. Both the time and the current flowing in the circuit was expected to affect the mass of copper deposited. However, the concentration of electrolyte was expected to have no effect. It was discovered in this investigation that both the time and the current was directly proportional to the mass of copper, and indeed the concentration had no effect. It was also found that due to the technical difficulties in measuring the gain of copper at the cathode, the loss of copper at anode was measures, since the two values should be the same. Method The beaker was filled with 100 ml of saturated solution of copper sulphate at 20oC. The electrodes were made by cutting 0.5 mm sheet copper into size (1 in x 6 in). The electrodes were sandpapered prior to use in order to remove the oxide layer on the sheet copper. This was attached to the side of beaker by bending the electrodes into shape so that it clings onto the side of the beaker. One of the electrodes was marked "+ve" with a compass. This was connected to the positive end (+5V) of the Power Supply Unit (PSU). The other electrode was marked "-ve" and was connected to the 0V terminal. The ammeter and the variable resistor was connected in series between the anode (+ve) and the +5V PSU terminal (Figure 1.1). After switching on the PSU, the apparatus was fiddled about by means of changing the voltage on the PSU and twiddling the knob on the variable resistor until a steady reading of 1.0A is obtained on the ammeter. ...read more.

Conclusion

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. 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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