The Electrolysis Of Copper Sulphate Solution Using Copper Electrodes

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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 5º 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. The size of the electrodes was also never exactly the same, as they were reused, so the amount of electrolysis differed from experiment to experiment. The separation of the electrodes was a small source of error, as they were not always exactly the same distance apart. The current which was controlled with the rheostat was not always the same, as the amount of copper decreases, so does the resistance, and so the current increases. Other errors could have been caused by the apparatus, such as the ammeter, which is quite old, and may not be perfectly calibrated, and the scales, which only show the mass to 2 decimal places. The rest are cut of with out rounding. Therefore this experiment could have been made more accurate by using lower current values, with the same size and separation of electrodes, controlling the current so that the temperature is constant, and the current more accurately controlled, and using a more accurate ammeter and a balance which rounds the other decimal places. My results showed many inaccuracies, shown by the accuracy bars on the graph (green for anode, and red for cathode). Which show the highest value and the lowest, with the average in the middle. This shows that for the 0.20A reading, the anode difference is 0.01A, and the cathode difference is 0.02A, both very small variations. For the 0.40A reading, the anode difference is 0.07A, a much greater difference, and the cathode variation was smaller, at 0.02A. The 0.60A anode difference was only 0.01A, and the cathode was the same. The 0.80A anode and cathode variation were also 0.01A. The final reading, 1.00A anode difference was 0.03, and the cathode variation was 0A. This nearly fits the pattern of the greatest variation being at the top, except for the 1.00A cathode variation of 0A. This increasing variation is caused primarily by two things, firstly the temperature of the solution increases more at higher current values, so the ions travel faster, and so do not stay on to the anode as well, and secondly the increased current itself has the effect of making less ions sticking to the cathode. The anomalous result for in the 0.40A value for the anode was probably caused by one or both of the crocodile clips touching the solution, so less electrons flow through the copper, and so less are transferred to the cathode.

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The range of my results were from 0.20A to 1.00A, with an average discrepancy of 0.02A from the average reading, which although there was one large anomalous result is quite small, is quite a small variation, therefore The evidence is strong enough to say that the mass lost at the cathode equals the mass gained at the anode, and that q µ i, as the greatest error was only 0.01g, or 12.5%.

If This experiment was to be done more accurately, I would have to use more accurate apparatus, such as a newer ammeter, a balance with more digits, a ...

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