In a experiment that dealt with electric conduction of many concentrated solutions, NaCl(s) created an unknown, to me, substance after adding a drop or two of water. Furthermore, it isn't the reaction of water and NaCl(s) that I don't understand, but the reaction between the anode and cathode when they came in contact with NaCl(aq), sparks were present and it seemed to have "burned" NaCl(s). The question is: what is the correct name for the part that "burnt"?
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1$\begingroup$ Nothing was burnt. You have just had a dangerous experiment. Apparently you have connected the two electrodes to a generator before dipping them into the solution. If an electric spark happened when touching the solution, it means that, before touching the liquid, there was a tension between the electrodes and no current. This is dangerous. You also may have been crossed yourself by an electric current. With wet hands, you may have been dead. You should never do this. Please put the electrodes into the solution before engaging the generator. $\endgroup$– MauriceDec 12, 2020 at 10:05
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$\begingroup$ What kind of voltage did you apply here? $\endgroup$– KarlDec 12, 2020 at 20:43
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$\begingroup$ Not sure what is wrong with this question! Have you never seen sparking of closely placed electrodes in electrolytes? $\endgroup$– AChemDec 13, 2020 at 4:13
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$\begingroup$ To answer both questions at once: the voltage was your normal household voltage, well at least I think it was; the professor asked us particularly about what the "burnt" part of the salt was and she also added, in the question, why were there sparks, that was my reasoning. $\endgroup$– MateDec 13, 2020 at 20:07
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$\begingroup$ @Mate, Your question was initially voted to be closed. My comment was for the folks voting to close it. Your query was okay. $\endgroup$– AChemDec 13, 2020 at 20:23
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1 Answer
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There is not "burning", one might see a spark. It is a well known phenomenon. Do you see lightening in the sky? Air is an insulator, yet when very high voltage is present it becomes a conductor. It is called dielectric barrier discharge. In the same way, discharge between two electrodes can occur in pure water (almost an insulator). Adding NaCl to water makes it a good conductor but still it is mostly water, and if the electrodes are close enough, electrical breakdown can occur. Instead of ions carrying the current as it should happen in an aqueous conducting solution, the current becomes electronic even in the presence of water. Apparently, the local heating between the electrodes is so high, that a gaseous plasma is formed between the electrodes and plasma are electrically conducting.
As suggested in the comment, always exercise cause caution and all experiments should be done under proper supervision by a trained person/teacher.
