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March 29, 2024, 02:20:54 am

Author Topic: Experimental design in electroplating  (Read 5523 times)  Share 

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Justanotherhuman

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Experimental design in electroplating
« on: May 20, 2019, 02:51:11 pm »
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Hey guys,
In class we did an electrolysis practical investigating on how time of current passed through cell affects the mass lost at the anode.

Experiment:
With 2 copper electrodes and Copper nitrate solution, we measured the mass lost at anode at 4A and 0.77V . We would measure the mass of the anode at 30, 60, 120, 180 second mark and did this trial 3 times. Before measuring, we would dip the electrode into ethanol and then water and wait for it to dry.

I'm trying to identify all possible errors that could have taken part. I noticed that their was an instance where the anode mass was constant even after 30 seconds of electrolysis :o

But here are the errors I can think of:
- The equipment was not calibrated (which is a systematic error)
- Overestimated weight: After dipping into water, the electrode was not fully dried
- Underestimation of weight: The electrical supply was not connected properly
- Overestimated weight: The negative and positive power supply reversed
- Contamination of electrolyte or impurity in electrode (not cleaned properly, is it enough to say it would simply interfere with the reaction, for example we found that our steel wool that we used to clean the electrode was in the electrolyte)
Is there anything else you can think of?
When writing a discussion or being asked questions regarding this experiment, what else could be discussed?

In order to limit errors, is the only thing we could do more trials?

Also, what is the different into amps and voltage, how does it effect electrolysis
Why is the anode dipped into ethanol and water before weighing?
We did 3 trials and did not change the electrolyte, how does that effect the experiment?
Does having an "open environment" have anything to do with errors that could have taken place?
The distance between electrodes was not kept same at all in the trials, does that have an effect?

Thank-you chemists!
« Last Edit: May 20, 2019, 03:09:07 pm by Justanotherhuman »

briv01

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Re: Experimental design in electroplating
« Reply #1 on: June 06, 2019, 11:27:23 pm »
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Some other extraneous variables that may have impacted upon the results as well as sources of errors are:
- concentration of the electrolyte-needs to be kept constant
-the distance between electrodes
-The temperature of the electrolyte
-possible side reactions that may have consumed reactants or contaminated the electrodes
-if the electrodes were impure and had contaminants ( using sandpaper before is a good improvement )
-if the anode was connected to the correct terminal, vice versa ( anode needs to be connected to positive terminal, cathode to negative )
-if the current itself passed was kept contant ( constantly measuring current and calculating average is a good idea for results, )
-the voltage of the cell, if voltage is too high, it may result in side reactions, also if voltage is above 2.06V, water may react leading to O2 and H2 production
-if equipment was calibrated ( systematic error  as you mentioned )
-the electrodes, mainly cathode needs to be measured initially, not just at intervals
-same SA and shape of electrodes in each trial


In the discussion, I’d say it’s good to discuss limitations ( even you having to use the same wool that you used to clean the electrode? I’m guessing you had no extra wool ), errors ( i think it’s good to mention what kind eg systematic or random ),  extraneous variables as mentioned above and some of yours, and improvements for these ( mainly controlled variables, repeating experiment ), and relating your results to the theory behind all this ( eg longer time means more electroplating )

Not changing your electrolyte for all trials is also bad as it may have been used up ( 1) or it may contain contamination from eg side reaction of the previous reaction

Amps affects the results as the Q is amps times time, therefore,it affects the calculation of the mass deposited