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For example, I want to purify copper. So the anode will be impure copper and cathode will be pure copper. However, instead of using copper sulphate/halides/nitrate solution, can I use magnesium chloride?

My thought process: Magnesium is more reactive than copper, so copper from the anode that are oxidised into Cu2+ ions will still be preferentially discharged, therefore not affecting the reaction(?).

Sorry if there are conceptual errors here and there, Im just really confused about this topic. T_T

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    $\begingroup$ There will not be enough chlorides for both magnesium and copper and it will probably end forming insoluble basic copper salts or oxides/hydroxides. Plus, there can be loses of chlorine. $\endgroup$ – Poutnik Mar 30 '20 at 10:17
  • $\begingroup$ If you use magnesium chloride in solution, you will not get any copper deposited on the cathode ! You will get $H_2$ instead. Is it what you want ? $\endgroup$ – Maurice Mar 30 '20 at 10:23
  • $\begingroup$ As others have noted, what you want to do is problematic, but it is also an opportunity! You can purchase copper sulfate quite inexpensively, so why not do the experiments? First, try the magnesium chloride electrolyte and carefully observe what happens at each electrode. Does the copper cathode increase in mass, due to adherent deposited copper? Then do the same experiment with the copper sulfate electrolyte. Again carefully observe what happens at each electrode. Are any gases evolved in either experiment? Just test your intuition! $\endgroup$ – Ed V Mar 30 '20 at 12:55

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