I will repeat this experiment with the following different voltages: 4,6,9 and 12 volts, and record the same voltages twice, each on a different rod– cathode and anode.
Method– Fixed Voltage
- I will set up the apparatus as shown on the diagram on the last two pages.
- Because the maximum amount of liquid a mini electrolysis cell can hold is 20ml, I will pour 18ml of water and 2ml of acid into it.
- After that I will fill the mini test tube with water and hold it upside down carefully, in a way that the water will not pour out.
- With that full mini test tube, I will put it in the liquid concentration of the mini electrolysis cell making sure that the open side of the tube is about half way down one of the rods which are sticking out. I will have to hold the tube while the reaction is taking place once I turn the power cell on.
- After that, I will turn on the power supply on and to 6 volts which at the same time a partner or friend of mine must start the stop-clock.
- Then I’ll wait until the gas that is being produced will fill up the tube with air right to the bottom of it’s mouth.
- Once it is clearly visible that the tube is full of air, I will stop the stop-clock and record the time.
I will repeat this experiment with the following different acid amounts: 4,6 and 8ml which in return will reduce the amount of water as the amount of acid gets higher to equal to 20ml. And also, I will record under the same fixed voltage along with each acid amount twice, each on a different rod– cathode and anode.
Risk Assessment
These points listed below are there to keep safe while experimenting and to ensure the use of the equipment again more likely.
- Avoid spilling acid on skin clothes and especially eyes.
- Goggles are recommended but not compulsory.
- Treat the mini electrolysis cells with care as they are liable to break and come at a high cost.
- Do not grip forks around the mini electrolysis cell with the clamp stand by means of too much force because it will cause the glass to crack or shatter.
Control
This whole experiment is to be done with control to make a fair test. To do this I am making sure that there is not an obvious change in temperature by getting the main substance, which is water, always from the same source. Once I have done one experiment at a single variable, I will use new acid and water for the next test because the used substances have already discharged most of their ions and so the effect won’t be up to it’s full potential in the next test. An ammeter and a voltmeter will be used to make sure that the power supply is in order and there is a constant current flowing as well as there being a potential difference.
Conclusion
The results that I obtained support my prediction which was that the more amount of acid increased the rate of electrolysis. The rate of reaction was also quickened by the increase in voltage.
The graph for the fixed acid amount shows that the effects on the cathode in changing the amount of acid is much more drastic than the anode as shown by the steep curved line. Towards the end of the lines they both show more or less the same pattern. The same goes for the fixed voltage graph.
Overall the cathode mainly had the quickest reaction for both graphs. This is because acid is short of negatively charged ions and therefore is a positively charged substance. Being a positively charged substance, there were more ions attracted to the cathode and as a result produced the most gas. The acid had, in a way, acted as a catalyst and so the increase of acid had obviously made the reaction quicker.
As I increased the voltage, the potential difference between the two electrodes became stronger according to the amount and so the discharge of the molecules, as a result of being attracted to their opposite charges, were at a quicker rate.
Evaluation
My experiments where split over many lessons and so inevitably something had changed making my results quite unfair. Although there were experimental errors, some of them were unpredictable such as the change in concentration and the temperature which may have slightly affected the results. To make sure this doesn’t happen again, I am considering to keep the same bottle of acid from the source it came from. Each lesson I had used a different mini electrolysis cell having the electrodes at different exposures and along with irremovable stains from previous experiments still attached to them. To improve this it would be imperative to use the same cell for each set of results. Using a Ammeter had greatly reduced my inspection for any predicaments during tests. With its help I knew there were no current failures or decreases and although the actual ammeter itself might have resisted the flow of current it is far too little to worry about. As the amounts of acid were being measured and then poured in they had left some water to its last dregs from not being poured in properly. This may have also caused some slight errors especially when it came to experiment on using 2ml of acid knowing that almost every drops counts for this being such a tiny amount.
There was one obvious anomalous result and probably due to some large unnoticed amount of gas being formed at the top of the mini test tube during the process of tipping it upside down without spilling any water. The anomalous result shows a decrease in time and so this gas formed at the top, as previously explained, had given it a sort of head start and finished earlier.
My results have no major distinctive errors and so they are reliable. More precautions to improve the experiment could be taken such as: using the same concentration of acid, keeping the same electrolysis cell in use, making sure there is no gas build up in the mini test tube before the experiment takes place, Pouring out the most of what there is out of the measuring cylinder and making sure there is no rust on the crocodile clips as it will decrease the current.
Extending the experiment would give a better understanding on how it works and the effect it has on different variables. After finding the results for different amounts of acid I could extend by changing the concentration and go to the other extreme by using an alkali. The electrodes could be changed in having different surface areas. Changing the temperature would also be interesting already knowing that it has already somehow affected my results and already having a rough prediction what would change.
