Why is this?
From my scientific knowledge I know that, in the electrolysis of a solution; the positive ions will be attracted to the cathode (Cations), and the negative to the anode (Anions). These two events happen at the same rate. Gradually, with the transfer of electrons, the anode is reduced in weight (and mass), the cathode on the other hand, increases in weight (and mass).
Safety
To keep my experiment safe I shall:
- Conduct the test standing at all times.
- Only alter the circuit when the power is off at the mains.
- Follow the standard laboratory safety guidelines.
Equipment
- 1 Power pack (electrical supply)
- Electrical wires and crocodile clips
- 1 Ammeter.
- 1 Variable resistor.
- 2 Copper electrodes.
- Copper Sulphate solution.
Measurements
I shall be measuring the current, as already stated, on the ammeter (using the variable resistor) and The weight of the two electrodes before and after a 10 minute period of electrolysis.
I shall repeat each of the experiments twice, finding the average and using it in both the table and graph.
Fair test
To keep my experiment a fair test I shall:
- Use the same equipment.
- Keep the concentration of Copper Sulphate solution the same.
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Make the time length precise and constant.
- Change only the current and the copper electrodes.
Prediction
I predict that by increasing the current, the rate of electrolysis will increase. My reasons for this are:
- By increasing the current the strength of the electro magnet at each electrode is also increased, so this should attract ions at a faster rate.
- If current had nothing to do with the rate of electrolysis, there would not be power plants situated next to every place where this process is carried out industrially.
Results
(g) (mg/amp)
average weight change against current. This shows that the results approximate to straight lines although several points appear anomalous. The line of best fit has been drawn for each set of average weight gain/loss results. These display a near mirror image between each line. The slope of these lines of best fit are 200mg/amp which compares, within the limits of the experiment, with the average slope determination 182mg/amp from Table 1
Conclusions
From my results:
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I have discovered that an increase in current leads to an increase in the rate of electrolysis. This can be seen not only in my table of results but in my graph.
- It is possible to observe that the relationship between the current and the weight increase on the cathode is proportional to the current; however, at the anode it is inversely proportional.
- ie increasing the current increases the weight change at the electrodes
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I can conclude that my predictions were correct, as confirmed by the proof above.
The increase in current causes a stronger magnetic field to be formed around each electrode. This pulls ions to the electrode at a faster rate (this applies to both electrodes), which consequently increases the rate of electrolysis.
This is the electrolysis of Copper Sulphate solution and I have proved that the rate of electrolysis is proportional to the current strength.
Problems
At first I had problems keeping the two electrodes apart. Fortunately by bending the electrodes over the side of the beaker this problem was resolved.
Accuracy
As the graph shows (through the lines of best fit) weight gain at the cathode is matched by the weight loss at the anode. The most anomalous results are highlighted on the graph.
These anomalous results could be explained by any of the following reasons:
- Drying the electrode too vigorously (removing some of the gained copper)
- Not drying the electrodes properly (increased weight – water)
- The balance did not have sufficient accuracy for the measured weight range
Possible alterations
improved and
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The experiments could be repeated more times, and therefore gaining a higher degree of accuracy in the average.
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By introducing a drying press we could remove a major variable of level of drying the electrodes.
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set at constant separation the between experimentsif different to start with could measurements when comparing one experiment with another.
Viewpoints of my experiment
I could also:
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Test this experiment using other solutions.
- Test for the effects of a voltage increase.
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Run this same experiment over a split longer period of time (weighing each electrode in each interval, before continuing the test)This would show if the electrolysis rate would remain constant.
- Repeat the tests at higher temperature of electrolyte