[cemo95]

Hello chemistry enthusiasts,
I study physical engineering and as one of the physics internship experiments I have conducted an electrolysis experiment which aimed to find the electrochemical equivalent of copper.
I have written a report on it and for this particular experiment, relative error was 3,74% which is in my eyes pretty satisfactory.

To give some background on the experiment, as electrodes copper rods were used and copper sulfate was placed in an aqueous solution. 3 trials were conducted, each with increasing current (200 300 500 [mA]) and I weighed the liberated mass of material on the cathode, calculated the relevant statistical values such as standard deviation, absolute deviation, standard error, relative error etc. In the discussion part I was to comment on the outcome of this experiment as well as evaluate the error analysis, in which I felt like I did a poor job.

Thankfully I passed, but I am curious so I wanted to ask you what could, other than the weighing error (including the part where you rinse the rods as well), could cause the error in this experiment? Some error related to the energy source perhaps? Or in a more chemical way could something in the solution could lead to this?

Thank you in advance and have a great day.

[Borek]

current (200 300 500 [mA])

Definitely possible source of error, although not on chemical side. On chemical side there is always possibility of side reactions.

[Corribus]

General sources of error can be speculated upon but with such a vague description of your procedure and equipment it's pretty hard to offer a good analysis. Even procedural things like the order in which replicates are measured can make a difference in data quality. It's also important to look at individual data points rather than just averages and stds, which can hide trends in individual data points that give clues about systematic errors and their potential causes. Just as an example - if your three replicates, which are measured sequentially, display an obvious trend (increasing values from replicate 1 to 3), this may be due to some kind of carryover event or possibly an irreversible change in the electrode quality from one experiment to the next.

[cemo95]

Thank you kindly for the answers people. Really appreciate it. I always loved chemistry and during highschool was pretty succesful at it too. Unfortunately in my studies I had no chemistry whatsoever, so this was a good experience.