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An investigation into whether the voltage affects the amount of gas produced during the electrolysis of sodium chloride solution.

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Introduction

An investigation into whether the voltage affects the amount of gas produced during the electrolysis of sodium chloride solution. Prediction: I think that hydrogen gas will be produced due to the half equation 2H +2e -->H this will be produced at the cathode because opposites attract and the hydrogen ions are positive. At the anode I think that chlorine will be produced due to the half equation 2CL -2e -->CL the chlorine ions are negative so they are attracted to the positive electrode. I also think that as the voltage is increased the amount of hydrogen gas produced will increase this is because of a series of scientific equations: if the voltage is increased the current then is increased, this is because of ohms law, V=IxR, where the voltage is proportional to the current, if the current is increased the charge then increases because Q=IxT. The number of moles of electrons=charge -:- 96500, this is Faradays constant from his 2nd law. The relationship between the amount of substance deposited at an electrode and the number of electrons that are passed around a circuit (current) can be used to calculate the expected volume of substance produced at the electrode. To find the amount of hydrogen gas produced at the electrode we would multiply the number of moles of hydrogen gas by 24, this is the area that one mole of any gas will occupy. ...read more.

Middle

take averages Fair test points * Temperature- has to stay the same so it doesn't speed up the process of electrolysis * Time- the amount of gas produced could be increased or decreased depending on whether the experiment is done for a different period of time. * Molarity- if the solution of brine is stronger or weaker the rate of electrolysis could become faster or slower * Amount of solution- if there is more solution then there is more room for the electrons to flow across the solution as ions and more gas can be produced * The size of the electrodes-this has to stay the same because if there was a really short electrode this would produce less gas compared to a longer one. * Surface area of electrodes-It has to have the same surface area to stop more gas being able to be produced * The distance between the electrodes also has to stay the same as the ions would have to travel further and it would take a longer time than if they were really close together. * Between each experiment the electrodes need to be sanded down, there then won't be any substances on the electrode to make it harder for the ions to get through. ...read more.

Conclusion

I think that my results would support my conclusion to a high extent, the higher the voltage the steeper the graph got, I think this pattern would hold true at the extremes of the range. Evaluation This experiment was overall very accurate and the evidence obtained was very reliable. I repeated my results and took 6 measurements. When I did repeat my results I got similar ones that were very close to the line of best fit. I had one anomalous result which may have been because I used a different bottle of brine this could have been a different concentration or the change from a plastic measuring cylinder to a glass one could have upset the experiment. To improve this experiment I would use a 25 volt lab pack with bigger measuring cylinders this would allow me to see if the pattern was still the same at the higher extremes of the range. Instead of using the measuring cylinder I could use a gas syringe this would be a lot more accurate. Another factor 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, I would get a new electrolysis cell, with clean electrodes which have never been used before. ...read more.

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