I’ve seen/done this experiment before as part of my middle school chemistry class, but now I have a question. How is it that the oxygen molecules all go up one side and the hydrogen molecules go up the other side. Presumably they both come from the same electrolicised water molecules, but then end up bubbling away separately an inch or so apart. Why don’t they just bubble up together from wherever they were divided?
This increasingly sounds like Chemistry middle school homework question.
Evaporation is a physical change. You’re describing a chemical change. As others have said, you’re “splitting” water.
Chemical equation is:
2 H2O (l) → 2 H2 (g) + O2 (g). The oxygen and hydrogen gas can escape when formed, so the water does disappear but not because it becomes water vapor. It becomes two brand new chemicals. This reaction doesn’t occur spontaneously, so you have to use the energy from a battery attached to electrodes. That’s what’s known as electrolysis.
Tyler DeWitt makes a lot of cute videos that can help you out with chemistry.
That’s because the oxidation of oxygen is happening on one electrode and the reduction of hydrogen is happening on another electrode.
https://images.slideplayer.com/23/6844583/slides/slide_59.jpg
It’s fun science you can do at home! IIRC I did it in my kitchen sink using tap water (which was a mistake. I should have gone with distilled) baking soda, an electrode from inside a D battery and the power from a few other D batteries. I got one test tube of hydrogen and one of oxygen. I also got weird green precipitate- presumably a form of copper. Hydrogen does indeed make a distinct sound when ignited.
Oh, for those who have trouble processing water as the product of burning- that’s why you can’t burn water. It’s already burned.
Thanks, Tfletch1. So it isn’t really H2O being blasted into H2 and O2, its H20 being blasted into H2 and some aqueous ions, then separately being blasted and being blasted into O2 and some different aqueous ions.
I’m a victim of lies to children.
Trust me, this isn’t homework. My middle school homework days are far behind me (except for the occasional nightmare, but then I’m not wearing any pants).
Note that the OP has been around since 2013. Only an occasional poster - 28 posts total so far, but clearly isn’t middle school age.
Well, you are DocCathode, after all.
Well, I guess blasting is going on but the blasting always involves electrons in bonds. The chemical reactions are happening right on the electrodes and the gaseous products (H2 or O2) float off each. One electrode blasts electrons onto each water molecule to make it an H2 molecule and aqueous hydroxide ion. The other electrode gets electrons blasted at it from the H2O when it turns into O2 and aqueous hydrogen ions (H+).
I like this analogy. To extend it, imagine that this is happening in one of those bars where the floor is covered in peanut shells. Nobody ever notices the shells you’re tossing out, in amongst all of the other shells. And likewise, if for some reason you didn’t care about the nuts, and just wanted a bunch of shells, you wouldn’t bother buying a bag of peanuts; you’d just scoop a bunch of shells off the floor.
In other words, electrolyzing water produces both hydrogen and oxygen, but nobody cares much about the oxygen, because we live in a place that already has oxygen all over the place. Hydrogen, though, isn’t just lying around for the taking, so we notice the hydrogen that’s produced.
Okay thanks
Submariners care. We threw the hydrogen overboard.
If this is about electrolyzing hydrogen to make fuel for fuel cells, it might be worthwhile to capture that oxy and sell it as industrial oxygen. Or it may not. Depends on cost vs market price.
Probably not. Next to liquid nitrogen, liquid oxygen is one of the most heavily produced industrial chemicals; hundreds of millions of tons per year (at <$100/t). Reclaiming it is unlikely to be cost effective unless you have a huge plant; one that competes with the scale of traditional air liquification plants (that produce liquid oxygen, nitrogen, argon, etc. all at once).
The title of your cite: “Is It Safe to Drink Hydrogen Peroxide?” Did I suggest drinking it?
I don’t know where gargling or sore throats came from. I used it for canker sores or minor oral infections.
There have been/are a lot of hydroelectric power plants that are used to just make hydrogen by electrolysis. The hydrogen has been subsequently used to make ammonia which in turn is used for making fertilizer:
-
in 2002, Iceland produced 2,000 tons of hydrogen gas by electrolysis
-
The existing Nangal plant in operation at the time of appraisal had a design capacity of 310 tons per day (tpd) of ammonia. Unlike most modern ammonia plants which usually rely on natural gas or petroleum derivatives as feedstock, it was based on water electrolysis.
Hydrogen is inefficient to compress (because of the small molecule size, trying to compress it results in significant energy wasted as heat), but it is a mature industrial process.
Oxygen on the other hand is a big no no when it comes to compression. With the right velocity and temperature, Oxygen will happily burn Stainless Steel, Incoloy …
In air separation plants, Oxygen is produced as a cryogenic liquid, the liquid is Pumped to higher pressure and the high pressure liquid is then vaporized to make high pressure gaseous oxygen.
So in short, there are no industrial compressors that will compress the oxygen coming out of an electrolysis plant; it’s safest to vent and that what happens.
Electrolysis isn’t just the splitting of the water molecule. It’s 2 different electrochemical reactions that happen specifically at each electrode. The cathode yields hydrogen (bubbles) and hydroxide (goes into solution). The anode yields oxygen (bubbles), 2 electrons, and 2 protons. Some of these recombine back into water, and some of them flow as electric current to the cathode.
So it’s two different, but interrelated reactions going on.
Well, as soon as water goes through the process, it becomes two separate gases and is water no more. The water that is left is water simply due to the fact that it hasn’t started the process as of yet.
Taking normal pressures / temps here.
Water always has H+ and OH- ions. In fact that’s the basis of pH
Let’s call concentration of H+ ions as CH and OH- as COH (Molar concentrations)
CH x COH = 10^-14 Always
You add acid to water, CH will increase and COH will decrease, but the product will remain the same
In Neutral water CH = 10^-7 and COH = 10^-7
The negative logarithm of CH is pH. So pH=7 for neutral water.
As electrolysis happens, if the ions are consumed, water will just make more of them since CH x COH = 10^-14
To extend the peanut analogy beyond its usefulness:
Imagine that in a bowl of unshelled peanuts there is at any time a few peanuts out of the shell and a few shells that only have one peanut in them. Peanuts are positively charged and shells are negatively charged, so they attract each other, and shells fill up, but there’s constantly a few peanuts popping out as well.
Now if you add a voltage by sticking two electrodes into the bowl the positive peanuts will be attracted to the negative electrode where they will accept electrons and bond together into gaseous peanut butter that will bubble out of the bowl. And the negative one-peanut-plus-shell will be attracted to the positive electrode where they will donate two electrons, lose the peanut and join another empty shell that just underwent the same process to form a small peanutshell butterfly, which is also a gas.
Hmm, maybe making the hydrogen gas equivalent to peanut butter was a mistake. Extending the analogy to burning hydrogen becomes very weird now.