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tribianni

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Hi. I need help with my lab report about error sources. I'm investigating the effect of concentration of cathode solution on cell potential. I constructed a basic voltaic cell and used 1, 0.5, 0.1, 0.05, 0.001 M CuSO4 solution. What are some possible error sources other than the fact that that experiment was not exactly carried out under 25oC 1atm ?

Also, is it a good way to leave the solutions for rest for a few minutes to make their temperatures equal with room temperature so that the initial temperature of solutions are kept constant through the experiment, for getting full marks on developing a methode to controll the variables criteria ? I cant find another way to control the temperature since adding ice would change the concentration of solutions.

Any comment will be appreciated. Thank you :D

Edited by dilara
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For controlling temperature, you can submerge the solutions in a bowl of water (given that the solutions are in a beaker of course), and let the solution and water reach room temperature. Water has a very high heat capacity, so you can safely assume that you've tried your best to control temperature.

Or like you had suggested, given that room temperature will not widely fluctuate, then simply leaving the solution to reach room temperature should be enough to control temperature. But you should explicitly state this in the "Method" section of your lab report (What you had done + what variable you are controlling/varying).

For the evaluation section, the sources of error will greatly depend on the experimenter. One thing that I would suggest you look at is the oxidation of electrodes, and how this can potentially affect your experiment.

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what is the reason for that oxidation? more cu(s) is collected around cu electrode but why does the zn electrode gets darker?

The oxidation that I was referring to was the reaction between copper and air (which creates copper oxide). Same with the zinc+air.

I'm not exactly sure why the zinc gets darker (during the reaction, I presume), but it probably has to with the solid zinc oxidizing into the sulfate solution. As the reaction progresses, the salt bridge attracts ions so that the redox reaction can go for extended periods of time.

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