[Music] hi I'm welcome back to free size lesson Scholl dot uk' by the end of this video you should be able to describe how to investigate what happens when aqueous solutions undergo electrolysis and this is a required practical so you need to learn the details now before we start I'd recommend that you watch the two videos on the electrolysis of aqueous solutions okay so in this protocol we're going to carry out electrolysis on two different aqueous solutions and explain the different products formed the two different solutions are copper 2 chloride and sodium chloride were going to start with copper 2 chloride solution first we pour approximately 50 centimeters cubed of copper 2 chloride solution into a beaker we then place a plastic petri dish over the beaker the petri dish you should have two holes we now insert a carbon graphite rod into each hole and these are electrodes now carbon graphite is unreactive so these electrodes are inert in other words the electrodes will not react one key point is that the two electrodes must not touch each other as that would produce a short-circuit next we attach crocodile leads to the rods and then connect the rods to the terminals of a low-voltage power supply we now select four volts on the power supply and switch it on now we need to look very carefully at the two electrodes if we look at the negative electrode in other words the cathode we can see that it's being coated with copper remember that if the metal is less reactive than hydrogen then the matter is discharged at the cathode now in this case copper is less reactive than hydrogen so coppers discharged at the cathode if we look at the positive electrode in other words the R node then we can see bubbles of a gas and we might notice the smell of chlorine in the air now remember that we're electrolyzing copper to chloride and chloride as a halide ion whenever we carry out electrolysis on an aqueous solution containing a halide ion then the halogen is discharged at the anode so that means that we're producing chlorine gas at the anode if we hold a piece of dumped blue litmus paper near the uh node then it becomes bleached and that proves that the gas is chlorine okay so to summarize if we electrolyze copper to chloride solution then we got copper discharge at the cathode on chlorine gas discharge at the Arnold now we're going to repeat the experiment but this time we're going to electrolyze sodium chloride solution so here's the apparatus we've placed approximately 50 centimeters cubed of sodium chloride solution into the beaker just like before we turn on the low-voltage power supply and we look at the two electrodes if we look at the anode first in other words the positive electrode we can see bubbles of gas being produced this gas bleaches dumped blue litmus paper and that tells us that the gas is chlorine sodium chloride contains the chloride ion which is a halide as we said before if we carry out electrolysis of a solution containing a halide ion then the halogens discharged at the anode we can also see gas bubbles at the cathode and this gas is hydrogen again that's because we're electrolyzing sodium chloride solution and because sodium is more reactive than hydrogen hydrogen gas is discharged at the cathode now we could prove that this gas is hydrogen by collecting it and then testing it with a lit splint hydrogen gas produces a squeeky pot remember you found plenty of questions on this required practical in my revision workbook and you can get that by clicking on the link above [Music]