The Electrolysis Of Urea

hi guys harry here welcome to scrap science [Music] before this video starts i did just want to warn you that this is probably the most boring and useless video i've ever made on this channel so you know i'm warning you um click away now or prepare for suffering um back to me after my last few videos what i really feel like doing today is a simple experiment you know an easy little video and i think i found the perfect thing to do to demonstrate today and that is the electrolysis of urea to generate hydrogen and nitrogen gases the experiment itself is pretty self-explanatory i think all we need to do is set up a solution of urea and then electrolyze it and we will be able to collect the hydrogen and nitrogen gases of our two electrodes so what we're going to do straight away is get right into it make up our urea solution and start electrolyzing to get our urea ready for electrolysis i have four grams of urea right here and 200 milliliters of distilled water um all we need to do is just dissolve that up in distilled water there and that might take a little while to dissolve anyway while that's dissolving as it is as a solution of urea in water it's not going to be conductive because urea is not an ionic compound so as a result there won't be any charged species in solution and we won't be able to perform our electrolysis directly on this solution here so to make the solution conductive all we need to do is add an ionic compound preferably one that is electrochemically inert to some degree and also preferably something that has a lot of hydroxide ions in it for reasons that i'll go over later the best option in this case is potassium hydroxide to add to our solution simply because it's extremely conductive i'm going to be using the next best thing and that is around 32 grams of sodium hydroxide because potassium hydroxide is a bit more difficult for me to get hold of so i'll just add a whole bunch of this maybe not all at once but eventually we'll get all that dissolved and there we are our solution is now ready for electrolysis now to do our electrolysis you can see what i have here is a youtube which is extremely handy when we're doing simple electrolysis reactions and we want to collect the gases that are coming off the electrodes so say we have our electrodes here is just a piece of nickel that we'll be using later they fit nicely just down the sides of this tube we can fill it up with our solution and the gases that are generated on the electrodes are separated and we can take off our gases through these little gas takeoff tubes that i've put on the end it is going to be really handy today so i'm just going to pour some of our urea solution straight into the youtube here now as you can see i have everything else set up i've put two electrodes into our youtube both of which are nickel i'll go over why i've chosen nickel as an electrode here in just a little bit and i have begun supplying 1.5 volts across our two electrodes so this one on the left is negative that'll be generating hydrogen gas and this one on the right is positive that will eventually be generating nitrogen and carbon dioxide we expect the carbon dioxide to react with the sodium hydroxide that's in solution here to form sodium carbonate so the only gas that should come off the electrode will be nitrogen gas anyway as you can see at this 1.5 volts we are generating hydrogen off the cathode you can see that bubbling off the electrode rather quickly there we have about six milliamps flowing through the cell right now so that's not much gas production but you can definitely see it there on the anode you can also see if you look very closely and you have set the video to a high resolution which you can do now with this video if you hadn't noticed you should be able to see tiny little bubbles of what we hope is nitrogen gas now you might be thinking well harry why don't you just increase the voltage in order to increase the rate of production of both of these gases and that's a good idea increasing the voltage will increase the current draw of our cell and then our reaction rates on both of our electrodes will increase however there's a problem with increasing the voltage past 1.5 volts and that is the fact that voltages much higher than 1.5 volts will start electrolyzing water itself to quite a significant degree you see while electrochemical splitting of urea is actually incredibly easy in terms of energy requirements thermodynamically the minimum voltage required to split urea is around 370 millivolts so 1.5 volts is definitely in excess there and the excess voltage is just going towards increasing that current all the way up to i think now we're approaching 7 milliamps the electrochemical splitting of water occurs at around 1.23 volts again this is the minimum voltage determined by the thermodynamics so the basic gist of it overall is that on nickel electrodes um urea can be split um electrolytically by voltages between 1 and 1.5 whereas above 1.5 volts we start to get electrolysis of water occurring and instead of generating exclusively nitrogen gas we start to generate oxygen alongside that and that's something i don't want to do because i actually want to collect the nitrogen and demonstrate that it is nitrogen gas that we're making here if we run our electrolysis at 1.5 volts which is what we're doing here according to a paper that i read recently about this process i'll link it in the description the anode gas containing mostly nitrogen will only be contaminated with about two percent oxygen gas which i think is perfectly all right anyway while this is slowly building up in terms of the current that we're drawing i will connect up some tubing to either one of these gas takeoff tubes and we will get ourselves ready to eventually collect the gases right it's been some time since the last scene but i completely gave up on the setup we had before with the tubing that we had connected to our gas outlets um i just wasn't able to collect the gases coming off the electrodes probably because i had quite a few leaks in the system and the slow gas production rate uh just meant that we just couldn't collect anything so i've redesigned our electrolysis apparatus once again you can see what we've set up is kind of similar to what's known as a hoffman voltammeter which is a common high school electrolysis demonstration piece of glassware where we have our two electrodes and then the gas is collected in glass tubes positioned directly above our two electrodes there you can see what i've done i painstakingly added our sodium hydroxide and urea solution to this vessel and i was able to get rid of all of the air in here so these two test tubes that i've stuck to the top of our youtube these are completely filled with solution there's no gas in them in fact there's no gas in this whole apparatus whatsoever we're connected to just a little reservoir of our solution so that the air from the atmosphere can't get in but as we fill up these test tubes with gases the solution will have somewhere to go so i think this is a much better setup because well we can tell there are no leaks none of the solution is escaping our apparatus and say we make this electrode the negative one this electrode the positive one i will generate hydrogen on the negative electrode nitrogen on the positive electrode and the gases will have nowhere to go except for into our test tubes where we can collect and store the gases for later use anyway let's get right back into it and we'll connect up 1.5 volts to the cell again negative on the left and positive on the right now once again we're not going to see much happening because this is an incredibly slow process i'm probably going to have to set this up overnight and wait for the gases to collect in their respective tubes but luckily for you the viewer we can just skip forward to when we've actually collected some gases so i'll see you then at the start of this video did i say that this was going to be a simple experiment and like an easy process because that was a really stupid thing to say if we have a look here i've been running this electrolysis for 24 hours now and look at all of this nitrogen that we have produced i reckon that's less than a milliliter is that focused amazing so yes after 24 hours of electrolysis we have made this much hydrogen i'd call that maybe five to ten milliliters and then this much nitrogen which you can barely see the gases aren't quite in their three to one ratio we expected uh to see three uh units or whatever of hydrogen and one unit of nitrogen after we completed our electrolysis but due to the fact that there are some side reactions occurring on the anode i think you can see just a little bit that the anode is slightly darker than the cathode and that's due to the fact that the nickel surface oxidizes slightly to generate some oxidized nickel catalysts on the surface which are still conductive and can still allow for electrolysis but they do subtract from our nitrogen yield anyway i was going to run this experiment until we had a test tube full of nitrogen gas and then you know demonstrate that it's nitrogen and not oxygen by attempting to do the glowing splint test and show that it doesn't re-light a glowing splint but from the fact that it's going to take around a month to fill up this test tube with nitrogen gas you know am i going to wait a month to fill up a test tube with fancy air no i'm not i'm going to give up on this process right now and it's easy to say just build a better cell you know move the electrodes closer together give the electrodes more surface area allow for a wider tube between the two electrodes so that all of the current doesn't have to pass through this thin bit of tubing down the bottom here and then i don't know make the cell bigger in general but if the process of generating nitrogen even just on this demonstration scale requires me to build like a custom cell for this electrolysis procedure like i'm not going to put that much effort in i mean nitrogen isn't really that special i just really wanted this to be a simple demonstration so we are just going to completely give up here and while this quantity of nitrogen is too small to test you are going to have to take my word for it that this is nitrogen gas or if you can't do that you will have to take the word of the paper i have linked in the description so look overall while it is perfectly possible to scale up this process and feasibly generate a reasonable yield of hydrogen and nitrogen in this highly efficient manner i'm just not going to do it it's not worth my time if you would like to see something like that i believe another channel robert murray smith who i will link in the description as well has a couple of videos about this very process generating hydrogen and nitrogen so you should probably check those out if you want to actually do this yourself more successfully other than that did we achieve what we set out to do i mean yeah we made a tiny little bit of nitrogen gas was it worth it not in the slightest um is this video even worth uploading to my channel i suppose my channel could do with a bad video or two i won't mind i promise my videos are normally a lot more exciting than this so hopefully i'll see you later

Channel: Scrap Science

Views: 36,026

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Id: Bp_UQ8y9vsU

Length: 13min 3sec (783 seconds)

Published: Mon Jan 31 2022