we've seen in our last couple of videos that electrolysis is a technique that we use to split compounds into their Elements which we do by passing an electric current through an electrolyte for this process to work though the ions in our electrolyte have to be free to move around so for insoluble compounds like most metal oxides this means that you have to melt them to make them a molten liquid however for soluble compounds like copper sulfate and sodium chloride we can just dissolve them in water to make our electrolyte so in today's video we're going to see how the electrolysis of these acurate Solutions works whenever you do an electrolysis experiment you're going to need a beaker full of electrolyte your two electrodes with a positive anode on the right and a negative cathode on the left a wire joining the two electrodes and a power supply in the middle now the main difficulty with the electrolysis of acurate solutions is figuring out which ions will go to each electrode this is because in acuate Solutions as well as the ions from the ionic compound like copper and sulfate ions there will also be hydrogen ions and hydroxide ions from the water itself because water in Solutions splits up into its ions to work out which of the ions will react with each electrode you need to know a couple of basic rules the cathode which is negative will attract the positive ions so the metal ion from the compound and the hydrogen ion from the water but importantly it will only discharge one of these ions and we have to tell which one it is the rule is that the ion of the least reactive element will be discharged so if we take a look at our reactivity series we can see that if the ions of any of these metals were present then the hydrogen ions would be discharged because hydrogen is less reactive than these Metals whereas if we had copper ions then the copper ions would be the ones discharged because copper is even less reactive than hydrogen over at the anode which has a positive charge we have a similar problem as well as the negative ion from our compound which could be something like a nitrate ion or a bromide ion would' also have hydroxide ions this time though the rule to decide which will be discharged is a bit easier if a halide is present so fluoride chloride bromide and so on then they'll be the one that gets discharged but if a halight isn't present then and it's always the hydroxide that gets discharged to see how all of this works let's see what would happen if our electrolyte was an acurus solution of copper sulfate the first step is to work out which ions would have in the solution from the copper sulfate we'd have copper 2 plus ions and S so4 2 minus ions then from the water because remember it's an acurate solution we' have H+ and O minus ions if you think about the negative cathode first it could either discharge the hydrogen ions or the copper ions so all we need to do is check our reactivity series and because copper is lower down on the list and so less reactive the copper ions will be the ones that get discharged so they'll gain two electrons from the cathode and form pure copper and because all of this is done at normal temperatures the copper will be solid so it actually accumulates around the cathode meanwhile for the positive anode it could either discharge the hydroxide ions or the sulfate ions so it would discharge the hydroxide because our rule remember was that it will always do the hydroxide ions unless halides are present so the hydroxide ions will give up their extra electron to the anode and they actually go to form oxygen and water the equation for this is that four o ions go to form 2 H2O 1 O2 molecule and four electrons before we finish let's try one more example where our electrolyte is aous sodium chloride in this electrolyte we'll have sodium ions chloride ions hydrogen ions and hydroxide ions so just like before to find which of our positive ions the cathode will discharge we look at our reactivity series and can see that hydrogen is less reactive than sodium so the hydrogen ions will be the ones that get discharged by gaining electrons and forming hydrogen gas meanwhile at the anode we have to pick between chloride and hydroxide ions and because chloride is a halide that would be the one that gas disch charged so it will lose electrons and form chlorine gas if you haven't heard yet you can find all of our videos on our website Cognito toorgle questions and pass papers and we track all of your progress so that you always know what to study next so sign up for free by clicking here or browse our playlist here on YouTube