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An investigation to discover how the mass of deposited metal is related to the current that flows through an electrolyte.

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Introduction

Sarah Lee An investigation to discover how the mass of deposited metal is related to the current that flows through an electrolyte An electroplating company needs to know how the mass of deposited metal is related to the current that flows through an electrolyte. I have been asked to investigate... Possible input variables The size of current, metal at the electrode, concentration of solution, surface area exposed to electrolyte and the time exposed the metal is exposed may effect the experiment. Possible output variables If I change any number of the input variables the mass of the metal deposited at the cathode and the mass lost at the anode will be affected. My input variable I have decided to change the current that I pass through the electrolyte. My outcome variable I will need to measure or observe the mass of metal deposited at the cathode. My control variable To make my experiment fair, I will keep the concentration of the solution, metal at the electrodes, surface area of the metal exposed to the electrolyte and the time the metal is exposed the same each time I do the experiment. Scientific knowledge In the electrolysis of copper solution with copper electrodes copper is deposited at the cathode. There are positively charged copper ions in the copper sulphate solution, which are then attracted to the negatively charged cathode and deposited when they combine with +2 electrons. ...read more.

Middle

Record in a table the results and plot the average readings on a line graph[N1]. This is a table to show the amount (in grams) of copper deposited on the cathode during electrolysis Trial 1 Current in amps Mass before Mass after Total increase Observations 0.5 2.15 2.17 0.02 The total amount of 1.0 2.17 2.28 0.11 copper is increasing 1.5 2.28 2.46 0.18 2.0 2.41 2.62 0.21 A lot of copper is deposited on the 2.5 2.62 2.82 0.23 bottom 3.0 2.85 3.09 0.24 Pieces of copper are moving slowly towards the edges of the cathode Trial 2 Current in amps Mass before Mass after Total increase Observations 0.5 3.09 3.24 0.15 Copper moves much more slowly 1.0 3.04 3.24 0.2 Not a lot of copper on the surface of the 1.5 3.24 3.41 0.17 cathode 2.0 3.41 3.57 0.16 Lots of copper deposited on the bottom 2.5 3.57 3.82 0.05 3.0 3.82 4.13 0.31 The solution is beginning to get warm Current in amps Total average increase in grams 0.5 0.85 1.0 0.155 1.5 0.175 2.0 0.185 2.5 0.24 3.0 0.275 I am confident with my recorded results because I have taken enough accurate, repeated trials and used the equipment accurately to make reliable evidence of my experiment. I have taken extra observations of my experiment at various stages to improve my experiment results. ...read more.

Conclusion

I also took time to zero the scales so the measurements would be more accurate. I checked the wires to make sure they were covered, I wore goggles throughout the experiment and I washed my hands before and after the experiment. I have made some observations as I was carrying out my experiment, during both trials, excess copper was deposited on the bottom of the flask of solution therefore the results varied greatly between the trials because the amount of copper deposited on the bottom varied between the two experiments. Also obtaining the results for the experiment spanned over a couple of one hour lessons, even though I was very careful when putting the equipment away while putting away the cathode small amounts of deposited copper rubbed off therefore our results do not look quite right. As I have commented before, I feel my results are very accurate as I carried out my experiment methodically and recorded my results in a clear way. We took readings spanning from 0.5 amps to 3.0 amps. At each point I repeated it three times. Because points on my graph show good correlation there isn't an 'odd' point. I took many results, which were repeated, so I am confident that there are enough results to support my conclusion. To improve my experiment I would use, instead of a paper cathode, a small cylinder cathode so I could collected more deposit, which would make better more varied results. Other than that I feel my experiment was successful. [N1] ...read more.

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