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Investigate the effect of the amount of sodium chloride, i.e. concentration gradient, in the aqueous solution on the electric current during electrolysis.

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Introduction

Planning Background When an electric current passes through sodium chloride solution, chemical reactions take place at both cathode and anode. If one passes through sodium chloride solution, there will be passage of ions moving through this solution. This results in positively charged sodium ions, which have been dissolved into the solution, moving towards the cathode and deposited there. At the same time, negatively charged chloride ions will be moving towards the anode and discharged at the anode. This is called electrolysis. Aim of experiment My aim is to investigate the effect of the amount of sodium chloride, i.e. concentration gradient, in the aqueous solution on the electric current during electrolysis. Key Factors/ variables that affect the results of the experiment The experiment carried out aimed to monitor the current during electrolysis when the amount of sodium chloride was changed. To ensure a fair test, only one of the listed key variables is allowed to change at a time with the rest of the variables are kept constant." This will give me an accurate set of results, which, I hope, enables me to make a decent conclusion. If we do not control the factors apart from the concentration we are testing, you can turn around and say that it was the other factors that had caused the difference and that it had nothing to do with the concentration. ...read more.

Middle

I don't think it's a large problem for me because a chose 5A for my experiment, unless I accidentally turned it the wrong way, I should not think that it will happen. Finally as this experiment involves electricity, electric shocks might occur. I will be careful and avoid possibilities of getting the shock, for example, using wet hands to touch the wires and before using the wire, check if it is safe, i.e. no holes. Sodium Chloride, i.e. salt, is not believed to present a significant hazard to health. Therefore, I do not need to be so cautious, but that doesn't mean being careless. I will wear safety goggles, if the electrolysis reaction is too vigorous. Evidence Collected My measurements of the experiment are shown in the table below: Concentration(g) First Test(A) Second Test(A) Third Test(A) Average(A) 5.0 0.22 0.22 0.22 0.22 10.0 0.42 0.33 0.31 0.35 15.0 0.54 0.34 0.39 0.42 20.0 0.59 0.38 0.52 0.50 30.0 0.60 0.57 0.58 0.58 I believe that these results to be accurate and reliable as measurements in the same tests are quite similar and they all go in sequence. All of the experiments follow the trend that the higher the concentration, the larger the current. E.g. At 5g, the current is 0.22A and at 30g, the current is 0.58A. ...read more.

Conclusion

This might contaminate the solution. I think I should use a new pair of electrodes when I do the repetitions. Also, I think I should have used the same top pan balance when weighing, as there may have been slight differences between the two balances. The above reasons are what could explain the anomaly in the graph. To further improve my experiment and add additional conclusive data, I would test a larger range of concentrations, for example, from 0g of sodium chloride to 35g of sodium chloride. This would give a larger range of data for me to analyse and draw a conclusion from. I can also, use a larger voltage, e.g. 8V. I used 5V in my experiment, but found that it did not give me a wide range of current. I gathered from other fellow students' investigations, that 8V has a better result. I am also quite interested in seeing what time has to do with electrolysis. I am considering this factor for further work. Actually, the result I gave in the observation part was my second attempt of getting the results. At first, I made a mistake by using the same solution 3 times to get the result. The results decreased after each attempt, therefore I realize that time must have something to do with the current. I think this is because if there is more time, the sodium ions will have more time to deposit. I can also investigate other variables such as temperature and surface area. ...read more.

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